Inheritance in Sweet Peas William Melville Fleming

Inheritance in Sweet Peas

William Melville Fleming IHHERITANCE I N SWEET PEAS *y

William Melvin Fleming

A Thesis submitted for the Degree of MASTER OF SCIENCE IN AGRICULTURE in the Department of HORTI CULTURE

THE UNIVERSITY OF BRITISH COLUMBIA APRIL 1925. ACKNOwTJEDGKLDSNTS.

The writer desires to express his grateful appreciation of the opportunities afforded for carrying on this investigation to the seed growers of Cowiohan and more particularly to Messrs A. & S. Matthews, of Weetholme, who gave valuable assistance in collecting notes in the field and to Messrs Crosland Bros, and Capt• Dobbie of Duncan, who extended many privileges in pursuit of these studie e» He Is also deeply grateful to Mr. George Robinson of Royal Oak, who made possible a greatly increased field of study by assistance in reoords on over 80 varieties, many of whioh were not grown in Cowiohan. He would further express sincere appreciation to Associate Prof* A.7. Bares, A.B.; B.8.; M.S. and to Assistant Prof. P. X. Buck, B.B.A. of the University of British Columbia, for assistance in planning and develop­ ing these studies, and also to Prof. A.H. Hutchinson, M.A. Ph. D. of the same University, whose suggestions for study In genetios proved a rich field of material and made possible the induction of valuable material that might otherwise have been overlooked. To Prof. R. C. Punnett, P. R. 8. of Cambridge University, who has probably done the most original research along the line of genetics In sweet peas, the writer is indebted for furnishing copies of available publications.

» 1.

INHERITANCE IN SWEET PEAS-

INTRODUCTION.

During the closing years of the war, Messrs Croeland Bros, laid the foundation of the sweet pea seed growing industry in the Cowichan Valley. TheBe men had "been members of the National Sweet Pea Society while still engaged in the manufacture of woollens in Yorkshire. On coming to Cowichan they continued to grow sweet peas and soon observed the possibilities in seed production. By the year 1919 they had increased their production until they had three acres in sweet peas and orders for seed were piling up. In 1920 they sublet a number of contracts and greatly increased their acreage. The same year, several inexperienced growers secured contracts and commenced to produce seed. During this year and the following year, the industry boomed. The acreage increased until it totalled between 25 and 30 acres and nearly 5° different growers were producing sweet pea seed in Cowichan alone. The seeds grown by the inexperienced growers in 1920 Here sold to British seed houses and were retailed in the spring of 1921. Complaints about the impurity of much of the seed began to paur into these British seedsmen and these were able to trace the source of the mixed seed to Vancouver Island. They looked with suspicion on all seed originating there and as a result, considerable difficulty was experienced in marketing the crop. In 1922 as a result the acreage was very materially reduced, the careless growers were refused con­ tracts and the more careful growers took all possible steps to improve the quality of their product. It was with the hope of being able to render assistance in securing purer strains of seed that these studies were commenced. Much of the material contained in this article has been gathered from information published by previous investigators and compiled in convenient form for the use of growers. Certain characteristics have been studied * more carefully and the results of these studies have been included. 2.

It will be seen that these findings are largely in the nature of a preliminary report. The need for further investigations has "been noted and an endeavor to suggest possible lines which these might follow has been made. 3-

HISTORY AND DEVELOPMENT. A Native of Sicily.

In 1699 an Italian Monk, Franciscus Cupani, sent some sweet pea seeds from Sicily to Dr. Uvedale at Enfield in Middlesex County, England. He also sent some seeds to Caspar Commelin in Amsterdam. One of the plants grown by the latter figured in a famous old botanical work. The Horti-Medici Amstelodamensis published 1697 - 1701. This plant was figured under the title Lathyrus distoplathyphyllus hirsutis, mollis et odorus. Burmann, Professor of Botany at Amsterdam, about thiB time caused some confusion by listing among plants native to Ceylon, Lathyrus Zeylanciue. It has since been established that the sweet pea is not native to Ceylon and that Sicily and Sardinia are the real homes of the sweet pea. Linnaeus gave the Sweet Pea its scientific title, Lathyrus odoratus. The sweet pea was first offered for sale in England by Robert Purber, gardener at Kensington about 173°• Early Types. The original type was a bicolor with purple standard and reddish blue wings. Only one flower appeared on a stem. During the first one hundred years of the history of the sweet pea, only three varieties or colors were known. a) Purple with blue wings, (b) Pale red with white wings. Painted Lady) and (c) White. All of these were known as early as 1731* Early Improvements. The first evidence of improvement is noticed in the catalog of John Mason, published in 1793* He offered black, purple, scarlet, white and Painted Lady. The black was probably a very dark purple as similar varieties are listed by Mawe in 1800 except black is listed as black purple. Page in 1817 refers to a striped variety which we find offered for sale in Carters list in 1837. A litt'le later the same firm offered a yellow variety. One wonders whether this was any nearer the coreopsis yellow than some of our modern "yellow" varieties. Until 1850 select- 4.

ion was for color only. In that year, Cooper and Botton listed a new Large dark purple variety. The first pea to present "blue coloring was the "Blue Hybrid" raised "by Major Trevor Clarke at Daventry and offered by James Carter in i860. This was a white variety with a well defined blue edge. It was therefore the forerunner of the Picotee edged varieties. It is said to have been the result of crossing a white sweet pea with the blue flowered Lord Ansons pea. Lathyrus magnellanicus. Between i860 and 1870 from Steven Brown of Sudbury, came Scarlet Invincible the first variety known to have more than two flowers on one stalk. Haage and Schmidt of Erfurt sent out Crown Princess of Prussia (light flesh pink) also with more than two flowers on a stalk. Carter, starting in 1867 with Imperial Purple (an improved purple) by selection over 13 years, was able to fix a reasonably black flower Invincible Black. Recorded Cross Fertilization. In 1883 Invincible Carmine was the first recorded result of crossing fertilization. The parents were a purple and a red variety. Between this date and 1800 a great many new varieties were introduced by Thomas Laxton and Henry Eckford. Worthy of note are Mrs. Sankey (1889) a pure white with black seeds and Lottie Eckford with small seeds, shrunken in appearance although possess­ ing plenty of vigor. Origin of Spencer Type. July 25 - 19°1# w*s a memorable date in sweet pea history. The first exhibition of the National Sweet Pea Society was held. Further Silas Cole, gardener for Earl Spencer exhibited Countess, a beautiful pink with frilled or waved segments. This was a sport from Prima Donna, a pure pink self. The seeds of this plant were secured by Robert Sydenham and chiefly sent to California for multiplying. The stock was not fixed and after being distributed in 1904 presented almost as many variations as it had admirers. In 1903 Silas Cole showed a new and distinct frilled variety, John *ngman, a rosy carmine and a very similar variety, Gladys Unwin, was produced by Unwin of a Histon and distributed by Watkins and Simpson. 5-

From 1904 to the present each year has fceen the introduction of numerous new varieties, many of which are very much alike. There has nevertheless "been a steady improvement in size, color and number of flowers produced on a stalk.

Winter Flowering. In 1889-90 Ant. C. Zvolanek introduced the first winter flowering Grandiflora Bweet pea. The grower claimed these resulted from cross pollenation of sweet peas with a common vetch, largely grown for fodder in Europe. In I9O3, he "began crossing his early flowering sweet peas with seeds of the Spencer varieties and "by 1907 was able to introduce winter flowering Spencers. These have "been crossed up with other Spencers until there is practically an early flowering variety for each type of Spencer. Telemly. In the I9O7 Sweet Pea Annual, an account of an early flowering sweet pea originating in Algiers as a sport from Blanche Ferry was given by Rev. Edwin Arkwright. This first plant appeared about 1900 and by crossing with other varieties Mr. Arkwright had produced some 18 varieties of this early,flowering type. This type although intro­ duced into England has never gained much importance there. Cupid. The dwarf or cupid sweet peas are varieties that grow only five to eight inches high with a spread of twelve to fifteen inches in diameter. The dwarfing has been accomplished by an extreme reduction in length of the internodes. The cupid sweet peas originated in 1893 at Santa Clara, California, on the grounds of C.C. Morse & Co. The plant was found growing among plants of the tall growing variety Emily Henderson (a pure white) Its characters were so fixed that when in 1895 Morse & Co. grew 7 acres of this novelty, none of the • plants reverted. A similar dwarf white was discovered in Erfurt, Germany, and was ready for introduction by 1896 but when Cupid was announced, it was declared to be the same variety to avoid confusion. In 1895 a similar dwarf 6.

appeared on the grounds of Henry Eckford at Wem, England. There is also some evidence that a similar form was found in 1895 among p-lants of the Old White grown in Southern France. This remarkable instance of synchronistic varia­ tion appeared in three or four widely separated localities within a period of two years. Singularly enough so far as known, all these dwarfs had white flowers and white seeds and developed among white varieties. # Pink Cupid was discovered among plants of Blanche Ferry in 1895 and was introduced by Burpee in 1898. He paid $1,000.00 for 1068 seeds in 1895. A yellow sport was found among White Cupid and introduced in 1899 as Primrose Cupid. From 1896 to 1903 a great many varieties appeared reproducing all the known types and colors of the tall growing varieties. Laxton Bros, of Bedford, England, began crossing Cupid with tall growing varieties and in 1900 had 23 varieties.

# Sweet Pea Studies III. A.C. Beal, Cornell, Bulletin 320 - 1912. 7-

PRINCIPLES OF INHERITANCE OP CHARACTERS. Explanation of Some Genetic Terms.

Except for the relatively rare instances of parthenogenesis a new individual whether plant or animal, arises as the joint product of two sexual cells derived from individuals of different sexes. Such sexual cells are known "by the general term of gametes and the individual formed by the fusion of two gametes is spoken of as a zygote. Mendel considered that in the gamete there was either a definite "something" corresponding to the dominant character or a definite something corresponding to the recessive character and that these somethings whatever they were, could not co exist in any single gamete. Por these somethings we shall use the term factor- The factor then is what corresponds in the gamete to the Unit Character that appears in some shape or other in the development of the Zygote. Mendel considered there was a factor corres­ ponding to the dominant character and another factor corresponding to the recessive character of each alterna­ tive pair of unit characters and the characters were alternative because no gamete could carry more than one of the two factors belonging to the alternative pair.

Mendel supposed the gamete always carried either one or other of such a pair. As experimental work pro­ ceeded, it became evident that this would not explain all cases.

Presence and Absence Theory. The "Presence and Absence" theory was put forward to explain the facts in a simple way. On this thBoJry the dominant character of an alternative pair owes its dominance to the presence of a factor which is absent in Hi f,**es8lve. The tall pea is tall owing to the presence in it of the factor for tallness but in the absence of this factor the pea remains a dwarf. All peas are dwarf but the tall is a dwarf plus a factor which turns it into 4 tall. Instead of the characters of an alternative pair being due to two separate factors, we now regard them as the express­ ion of the only two possible states of a single factor, its presence or its absence. A plant may now be said to be an organism whose » properties may be expressed in terms of unit characters. These unit characters are represented by definite factors in the gamete and the factor for any unit character is either present or it is not present. 8.

Interaction of Factors. There is further an interaction "between separate factors in the same gamete. This is clearly demonstrated in the sweet pea as follows. All white sweet peas breed true to whiteness. There are certain strains of white sweet peas which, when crossed together, produce only- colored flowers. For purposes of illustration, we may- take a case in which red flowers are produced. Red in the sweet pea results from the interaction of two factors and unless these are both present, the red color cannot appear. Each of the whites carried one of the two factors whose interaction is necessary for the production of the red color- Such factors are termed (COMPLEMENTARY) factors.

Atavism or Reversion. Reversion in general is a term applied to a sudden return to an ancient, generally wild form whether by hybridization or by some other cause. Many phenomena included under the term reversion or atavism can be explained satisfactorily as instances of complex factor interaction. When complementary factors which have somehow been separated are brought together, reversion or the reappearance of,the original type is bound to occur.

Mutations. A mutation is a heritable difference between parents and offspring which does not depend upon segragation and recombination. TOien a new variety suddenly appears in a standard variety without hybridization having taken place, it may look at first as if two complementary factors have been brought together but it is more probable that this change has taken place after the gametes have been formed. Punnett has proved # that the cretin mutation occurs in this way and is not a case of reversion.

# Note on the origin of a mutation in the sweet. R. C. Punnett, F. R. S. Journal of Genetics. Vol. VIII. No. 1. Dec. 1918. 9-

Mendelian Ratios.

When two characters are mated in the first or F 1 generation the offspring resemble the dominant parent. In the second or F 2 generation, the characters segregate in the ratio of 1 pure dominant, 2 heterozygotes and 1 pure recessive. This is the monohybrid ratio and may he illustrated in checkerboard $orm as follows. T represent­ ing tall sweet peas, t dwarf. T X t forms a simple heterozygote T t T t T TT Tt gives TT Tt Tt tt t Tt tt 12 1 When individuals heterozygous for each of two independent factors are crossed double heterozygotes are found in the F 1 generation. The gametes may be illus­ trated as AB; Ab; aB; ab. In the F 2 generation the character of the zygotes will be 9 AB; 3 Ab; 3 aB; 1 ab. This may be shown in checkerboard form. A B Ab a B a b A B AA BB AA Bb Aa EB Aa Bb A b AA Bb AA bb Aa Bb Aa bb a B Aa BB Aa Bb aa BB aa Bb a b Aa Bb Aa bb aa Bb aa bb

This is called a normal dihybrid ratio* Modifications of this ratio will be dealt with as they occur. Triple heterozygotes, that is,individuals heterozygous for each of three independent characters form eight types of gametes all equally numerous EG. Aa Bb Cc « ABC : ABc : AbC : aBC : Abe : aBc : abC : abC : In the F 2 generation these will give a typical trihybrid ratio of 27 ABC : 9 ABc : 9 AbC : 9 aBC : 3 Abe : 3 a Be : 3 abC : 1 abc : This may also be modified as will be illustrated later.

The Chromosome Theory. Every living organism is composed of cells filled with protoplasm. Each cell contains a number of nuclei. Each of these nuclei in turn contains a certain number of darkly staining bodies known as chromosomes. Although the cellB in different parts of the body may vary in size and appearance, all cells in plants of the same species or animals of the same species, always contain the same number of chromosomes (so called because they stain more deeply with various dyes than the rest of the cell protoplasm) There is always an even number of chromosomes in every body oell of an organism. The plant or animal grows by cell division. At each cell division each chromosome is very carefully divided in half so that the nucleus of each daughter cell has exactly the same number and kind of chromosomes as the mother nucleus. The exactness of this division in itself suggests that the chromosomes are bearers of hereditary characters since none of the other cell constituents seems to be so accurately divided at cell division. The behaviour of the chromosomes in connection with gamete formation is even more significant. When the organism forms gametes, a cell division takes place which is fundamentally different from cell division in ordinary growth. The chromosomes do not split but line up in pairs and the nature of the division is such as to draw apart the components of each pair. This reduces the number of chromosomes so that the resulting nuclei has just half of the characteristic number in the body cells. This is known as the (HAPLOID) number of chromosomes in contrast with the body cells which have the (DIPLOID) number. Gametes have just one representative of each pair that appears in the body cells. When two gametes unite at fertilization, there is a return to the diploid number.

As long as the known number of factor pairs does not exceed the number of chromosomes, it may he assumed that different pairs of chromosomes carry independent factors.

Linkage. Several different species of plants or animals have "been studied in which the number of factor pairs exceeds the number of chromosomes for that specieB. According to the chromosomes theory, some, if not all, of these chromosomes must carry more than one factor. This introduces a difficulty. Since the chromosomes must be supposed to preserve their individu­ ality, factors which occur on the same chromosome must always remain linked together. If they can be separated, we must either give up the chromosome theory or find some acceptable explanation for the inconsistency. T.H. Morgan and his associates working with the pomace fly Drosophila, have found evidence for over 100 factors while the number of factors is only four. Their experiments have shown that these numerous factors fall into four groups and they conclude that normally the characters in each group are all carried by the same chromosome. They term these characters LINKED CHARACTERS and the grouping LINKAGE.

Locus. Aft important point to note is the arrangement of the factors in the chromosome. This is assumed to be a linear one. Each chromosome may be regarded as a Btring of beads, each bead corresponding to a factor. Every factor has a definite fixed position or LOCUS in the chromosome. Theposition of any given factor in the chromosome always remains the same for all of the Individuals of the species. Occasionally it happens that two factors that are carried by the same chromosome become separated and give unexpected changes in the ratio. These are explained on a physical basis as follows. When chromosomes were examined by high power lenses, they were found to show all kinds of tangled contortions during the reduction divifiion. 12.

Crossing Over. A pair of chromosomes which normally lie side by side, may at times come to lie across one another. The portions touching may become fused and when they subse­ quently separate, they exchange that portion of the chromosome which lies beyond the point of junction. The result is factors which normally are carried on the same chromosome become separated. This process is known as crossing over. The nearer together factors are in a chromosome, the less likely they are to be separated. The further apart they are, the more often is separation likely to occur. It is upon the proportion of "crossover" gametes as compared with "non crossover" gametes that the distances between the factors along the chromosome have been determined, assuming that the factors are arranged bead like in linear position.

It is evident that linkage will cause modifica­ tion of the typical dihybrid ratio 9:3:3:1 since the four possible classes of gametes formed by F 1 individuals will not all be equally numerous. Accordingly the stronger the linkage, the greater will be the modifications of the typical ratio- Conversely we may estimate the strength of the linkage by the observed departure from the 9:3:3;1 ratio. Castle (Genetics and Eugenics, pages 120-122) gives the following tables to show. (a) The size of each F 2 class expressed as a percentage of the F 2 population. (b) The F 2 Ratio 9:3:3:1 as affected by coupling. (c) The F 2 Ratio 9:3:3:1 as affected by Repulsion (negative linkage) 13- A table to show the size of each F 2 Class expressed as a Percentage of the F 2 population. Table 1.

Percentage F 2 zygotes when

Ratio, cross­ and B enter together - A & B enter separately ing to non- (Table 2) (Table 3) crossover gametes AB Ab (or aB) ab AB Ab (or aB) ab 1: 1 56.2 18.7 6.2 56.2 18.7 6. 2 1: 2 6l.l 13-6 11.1 52.8 22.2 2, 8 l: 3 64.0 10.9 14.0 51 5 23.4 1, 5 1: 4 66.0 9.0 16.0 51 0 24.0 1, 0 l: 7.6 50, 7 24-3 0. 7 1: I ill 6.6 18.3 50, 5 24.5 0, 5 l: 69-3 5-8 19-3 50, 4 24.6 0, 4 l: 69.7 5.2 19-7 50, 3 24.7 0. 3 1: 9 70.2 4.7 20.2 50, 2 24.8 0, 2 1: 99 74.5 0.5 24.5 50. 0 24.9 0, 0 1: cx> 75.0 0.0 25.0 50, 0 25.0 0, 0

Table 2.

The P 2 Ratio, 9:3:3:1, as affected by Coupling or linkage, A and B Entering the P 1 Zygote in the same Gamete.

^tio, Cross­ Proportion P 2 Zygotes over to Non- Crossover AB Ab aB ab Total crossover Gamete8 Gametes.

2 l:z 3x + 2x ¥ 1 2xfl x2 (2x4-2)' c + 1 2(2x +• 1) 1:1 (a) 1/2 1 16 3 9 3 3 1:2 M 22 5 5 4 36 H3 1/4 41 7 7 64 1/5 66 9 9 J 100 1!1/4 1/6 97 11 11 144 ? 134 13 13 196 1:6 1/6 177 15 15 u 256 l: 49 1/9 226 17 17 64 324 l: 9 1/10 281 19 19 81 400 l: 99 1/100 29,801 199 199 9801 40000 1: Limiting Values (b) — JL (a) No coupling, (b) Not distinguishable from the case in which A and B are due to a single genetic factor. 14.

Table 3. The F 2 Ratio, 9:3:3:1 as affected by Repulsion (negative Linkage). A and B entering the F 1 Zygote in Different Gametes.

Ratio, Cross­ Proport ion F 2 Zygotes over to non- Crossov er crossover Gametes AB Ab aB ab Total Gametes 1 l:x x + 1 2(x2 4- 2x)f3 X2f2x x24-2x 1 (2x+2)2 1:1 (c) 1/2 9 j* -3 1 16 1:2 1/3 19 8 0 1 36 1:3 1/4 33 15 15 1 64 1:4 V5 51 24 24 1 100 l!J 1/6 73 3? 3£ 1 144 1:6 99 48 48 1 196 \% 129 6 1 256 III 1/9 163 £803 8J0 1 324 1:9 1/10 201 99 99 1 400 1:99 1/100 20,001 9,999 9,999 1 40000

Limiting Value 8 (d) — 2 1 1 Q 4

(c) No repulsion. (d) Not distinguishable from the case in which A and B are allelomorphs.

In a case where a double dominant mates with a double recessive and the result is a dihybrid ratio in the F 2 generation producing four types of gametes in the 9:3:3:1 ratio, there is no linkage but if the two factors are carried on the same chromosome and the F 1 generation produces only two types of gametes, then the F 2 generation will show a 3:1 ratio and linkage exists. 15-

APPLICATION OF PRINCIPLES OF INHERITANCE TO SWEET PEAS. Character Pairs in Sweet Peas.

Professors Bateson and Punnett in work with sweet peas at Cambridge, extending over a score of years, have contributed a great deal of information on the inherit­ ance of the different factors in sweet peas. Professor Punnett in a recent publication # describes seventeen pairs of characters showing normal Mendelian inheritance, as follows: In each case the dominant character of the pair is given first. (1) PURPLE A1 - RED a 1 (- B - b OP EARLIER PAPERS) While there are many shades of purple and also of red, only deep colors were used because other factors modify color. (2) LONG POLLEN A2 - round pollen a2 (« L - 1 of earlier papers) Long pollen when young is oval shape and contains 3 pores; round pollen contains 2 pores only. (3) ERECT STANDARD A3 - HOODED STANDARD a3 (: E - e of earlier papers) (4) DARK AXIL B1 - LIGHT AXIL b1 (= D - d of earlier papers) The dark axil is usually distinct but is relatively pale where the flower color is blue or blue red. (5) FERTILE ANTHERS B2 - STERILE ANTHERS b2 (= P-f of earlier papers) (6) NORMAL FLOWER B3 - CRETIN FLOWER b3 (= N - n of earlier papers) The cretin is a monstrous form socalled from its fancied resemblance to a gaping mouth with a protruding tongue. The straight stigma protrudes through the cleft keel; the standard and wings are usually smaller than the normal flower and fail to expand fully. *

# Linkage in the sweet pea Lathyrus Odoratus by R. C. Punnett Journal of Genetics, Vol. XIII. No. 1, March, 1923. 16.

(7) TALL E - CUPID e (= T-t of earlier papers) (Tall have long internodes, cupid have very short internodes) (8) COLOR F1 - R WHITE f1 (= C-c of earlier papers) C. white and R white complementary factors which must "be present to produce color when two whites are crossed. (Compare # 10) See also interaction of factors page 8. (9) PROCUMBENT F2 - Bush f2 (« P-p of earlier papers) (10) COLOR G1 - C WHITE g1 (= R-r of earlier papers) (See note on #8) (11) HAIRY C - GLABROUS c Normal plants have short stiff hairs giving a rough feel to the stem; glabrous plants are quite smooth. The difference is mofet noticeable in young pods. (12) TENDRIL D1 - ACACIA d1 The acacia leaved sweet pea has leaflets in place of the normal tendrils. Dominance is not always com­ plete. Fl plants from acacia X tendril have always shown an occasional leaflet replacing a tendril, while in F 2 besides normal tendrils, and acacias intermediate of various grades occur. Punnett offers an explanation of this that there are probably two factors instead of one. One factor T pro­ duces tendrils. I intensifies the tendrillur character when T is present but has no effect upon acacias. This remains to be investigated. (13) BRIGHT FLOWER D2 - DULL FLOWER d2. To the bright flowers belong the normal purples and reds those of the corresponding recessive dull series being blues and blue reds. In the deeper colors the bright and dull series are perfectly distinct. (14) SELF COLORED F3 - MARBLED f3. Corresponding to each self colored form is a recessive one in which the color is broken up by finely divided white marbling. The marble form must not be con­ fused with the flaked form. In marbled form the keel and the under surface, of the wings are white while in a flaked form these structures always show some color. The marbled form always shows the light axil but may carry the dark axil in which case it acts as a complementary factor. 17

(15) PURPLE G2 - RED PURPLE g2 See notes on origin of red purple after (ll) (16) CLAMPED KEEL H - OPEN KEEL h. (17) PURPLE B4 - MAROON b4 The type of maroon is that of the Dobbies maroon which is a recessive to deep purple. Punnett obtained a pure strain of red purple and crossed it with Robert Sydenham (a rich orange salmon self) to teBt for possible linkage in the shape of keel. In the F 2 generation appeared a Spencer form of red purple which was carried on the F3 generation. The same year, 1919, Dobbie brought out Dobbie^ maroon which appeared identical to Punnett*s. When tested out side by side in 1920, the two appeared outwardly alike and yet genetically were totally distinct as shown by crossing with the dull or recessive form of red purple. Punnett's gave a red purple in F^- and in F2 red purples and dull red purples in the ratio of 3J1« Dobbie1s maroon gave normal purples in P-L and in F2 besides red purples and dull red purples, various other shades of purple including some like the Pi normal purple, also some hooded forms and some normal blues. (18) Since publishing the article in March 1923, Professor Punnett published in September 1923. an article "The genetical analysis of the sweet pea, (Lathyrus odoratus)" in which he records crossing a mauve with the small spotted seeds of the mauve parent. In P2 came various shades of mauve and various shades of pink, the mauves to the pinks being in the ratio of 3«1« All the mauves had small spotted seed and all the pinks had normal seed. This suggested that spotted seed 1B a dominant character shewing close linkage with the blue factor in which the mauves differed from the pinks• This is of peculiar interest because if spotted seed is dominant to normal, the factor to viiich it is due has come into the sweet pea since it was taken into cultiva­ tion as the wild sweet pea has normal seed. To test the dominance, spotted seed was crossed with a purple with normal seed. P^ gave a normal seeded purple, F2 consisted of purples and mauves in the ratio 3'1« All of the purples, had normal seeds, the mauves had small spotted seeds. There­ fore the small spotted seed is a character inseparable from the mauve color of the flower and is not due to a separate independent factor. 18.

Interaction of Factors.

All white sweet peas breed true to whiteness. Generally speaking, the result of crossing different whites is to produce nothing but whites whether in F* or succeeding generations but there are certain strains of white sweet peas which, when crossed together, produce only colored flowers. The color may be different in different cases, but for our present purpose, we will take a case in which the color is red. wlien such reds are Allowed to self fertilize themselves in the normal way and the seeds sown, the result­ ing P*2 generation consists of reds and whites in the pro­ portion of 9 to 7* The raising of a further generation from the seeds of these P2 plants shows that the whites always breed true to whiteness, but that different reds may behave differently. Some breed true, others give reds and whites in the ratio of 3 to J. while others again give reds and whites in the ratio 9 to ?. The red in this case results from the inter­ action of two factors and unless both are present, the red color cannot appear. Each of the white parents carried one of the two factors whose interaction is necessary for the production of the red color. As a cross between them brings these two complementary factors together, the pi plants must all be red. Denoting these two color factors by C and R respectively, we may proceed to follow out the consequences of this cross. Since all the F1 plants were red, the con­ stitution of the parental whites must have been CCrr and ccRR respectively, and their gametes consequently Cr and cR. The constitution of the pi plants must therefore be GcRr. Such a plant being heterozygous for two factors produces a series of gametes of the four kinds, CR, Cr, cR, cr and produces them in equal numbers. The various types of zygotes produced, may be shown in checkerboard system as follows: CR Cr cR cr

CR CRCR CrCR cRCR crCR Cr CRCr CrCr cRCr crCr cR CRcR CrcR cRcR crcR cr Croft Crcr cRcr crcr 19-

An examination of this figure shows that nine of the sixteen squares contains "both C and R while seven contain C or R or neither, that is, 9 should &how color and 7 white. Further examination of the figure shows that the colored plants are not all of the same constitution hut are of four kinds viz: CCRR, CCRr, CcRr, CcRR. Since CCRR is homozygous for hoth C and R, all gametes which it pro­ duces must hreed true to the red color. A plant of the con­ stitution CCRr is homozygous for the factor C hut heterozy­ gous for R. All of its gametes will contain C but only one- half of them will contain R, therefore it will produce equal numbers of gametes CR and Cr. Two such gametes coming together must give a generation consisting of x CCRR, 2x CCRr, and x CCrr, that is, reds and whites in the ratio 3:1. Lastly, the red zygotes of the constitution CcRr have the same constitution as the original red made from the two whites and must therefore give reds and whites in the ratio 9:7. The existence of all these three sorts of reds was demonstrated by Professor R.C. Punnett and the proportions met with in the experiment, tallied with the theoretical explanation. As a further check, the F2 whites which came from a colored plant which itself had been produced by the mating of two whites was tested. An examination of the checkerboard shows that these are of $ different kinds, namely, CCrr, Ccrr, ccRR, ccRr, ccrr. None of these pro­ duce anything but whites on self fertilization. When crossed among themselves, different results were obtained as might be expected. The cross between two whites of the constitu­ tion CCrr, and ccRR gave nothing but colored plants,for these two whites are of the same constitution as the original two whites from which the experiment started. On the other hand, the cross between a white of the constitu­ tion ccrr and any other white can never give anything but white, for no white contains both C and R or it would not be white, and a plant of this constitution cannot supply the complementary factor necessary for the production of color,. Again, two whites of the constitution Ccrr and ccRr when crossed, should give both colored and white flowers in the proportion of 1:3. 20.

REVERSION. Reversion with Two Factors.

The sweet pea supplies a good example of reversion in structural characters. The Cupid sweet pea is a dwarf variety in which the intemodes are very short and the stems few in number. The stems are only 9 to 10 inches long. They diverge and lie prostrate on the ground. The Bush variety has numerous stems which do not diverge hut grow up side by side forming a compact bush. It grows 3"i" to 4 feet high. Bateson and Punnett crossed these with the un­ expected result that in pi generation all the plants revert­ ed to the ordinary tall sweet pea. The p2 generation con­ sisted of tails, bushes; Cupids with procumbent stems and Cupids with compact bush habit. These four types appeared in the ratio 9t3:3:l^

Bush X Cupid I Tall -11

Tall Bush Cupid Procumbent Cupid Erect P 2 9 3 3 1

There is here an interaction of two characters. Long internode (T-t) and procumbent habit which is dominant to erect (P-p) Since both plants carried shortened intemodes, the parental plants must have been ttPP and TTpp respective­ ly and their gametes PT; Pt; pT and pt. The Cupid variety might be represented by tP The Bush H " H " " Tp The cross may be shown in checkerboard. PT Pt pT p_t PT PPTT PPTt PpTT PpTt Pt PPTt PPtt pPTt Pptt pT PpTT PptT ppTT ppTt Pt PpTt Pptt ppTt pptt Tall procumbent forms TP = 9 Bush erect " Tp = 3 Cupid procumbent M tP a 3 Cupid erect H tp • 1

Reversion with Three Factors.

# when some white flowered varieties are crossed there are produced not red flowered Fl plants as described previously but purple bicolor. This reversion involves a third independent factor for blue B which is ineffective except in the presence of both the color factor C and the red factor R. when in such reversionary crosses a colored F^ is produced which is heterozygous for all three factors F* shows a peculiar modified trihybrid ratio. If one white parent contributes the color factor while the other contributes the red and blue factors, then we may represent the parental gametes as Crb and cRB respectively. 3?1 will then be a triple heterozygote CcRrBb which from the combined action of the three dominant characters will be a purple bicolor. Its gametes will then be of eight sorts and the zygotes in which corresponding groupings of the dominant flactors are shown in checkerboard system below• CHB CRb CrB cRB Crb cSb crB crb CRB CRB CRb CrB cRB Crb cRb crB crb CHB CRB CRB CRB CRB CRB CRB CHB CRb CRB CRb CrB cRB Crb cRb crB crb CRb CRb CRb CRb CRb CRb CHb CRb CrB CHB CRb CrB cRB Crb cRb crB crb CrB CrB CrB CrB CrB CfB CrB CrB cRB CRB • CRb CrB cRB Crb cRb crB crb cRB oRB cRB cRB cRB cRB cRB cHB Crb CHB CRb CrB cRB Crb cRb crB crb Crb Crb Crb Crb Crb Crb Crb Crb cRb CRB CRb CrB cHB Crb cRb crB crb oHb cRb cRb cRb cRb cRb cRb cRb crB CRB CRb CrB cRB Crb cRb crB crb crB crB crB crB crB crB o8B crB crb CHB CRb CrB cRB Crb cRb crB crb c rb c rb c rb crb crb crb crb crb

# Genetics & Eugenics, Page 118. (Castle) 22.

From this it will "be seen there are 27 CEB purple : 3 Orb white 9 CRb red : 3 cRb white 9 CrB white / 3 crB white 9 cRB white : l crb white

Only two of these eight groups contain combin- ations of factors capable of producing colored flowers viz: CRB which will produce purples and CRb which will produce reds; all the other six combinations lack one or both of the two factors C and R which must be present together in order to produce colored flowers. 'Consequently, all will produce uncolored (white flowers) The results will be twenty-seven purple, nine red, twenty-eight white, a modification of the normal trifcybrid ratio of 27:9:9^9: 3^3: 3:1 •

Coupling and Repulsion. In sweet peas purple and red are alternative color forms and long pollen and short pollen are alterna­ tives as to pollen shape. If a purple plant with long pollen is crossed with a red plant having round pollen four classes are obtained in 7 2 viz: purple long; purple round; red long; and red round. This being apparently a dihybrid Mendelian cross, we should expect the four classes to be respectively 9:3:3:1 "but in reality the classes purple long and red round are in excess of these proportions Bateson and Punnett discovered this in 1906 and explained the variation by saying that coupling exists between the characters purple and long and also between their alleolmorphB (contracting characters) red and round. Their experiments showed

Purple Long Purple Round Red Long Red Round 4-831 390 393 1338 (4814) (408) (408) (1332)

This is practically ay - 1 - 1 - 7 ratio which would give the results shown in brackets. 23-

Corroborative evidence was also obtained by crossing red round plants with the pollen of F 1. This method of crossing with the double recessive affords a direct test of the nature of the gametic series and the actual numbers obtained viz: 5° purple longs; 7 purple rounds; 8 red longs; and 47 red rounds, tallied closely with expectations. Later, however, when a cross was made between purple round and red long, it was found that these combin­ ations were in excess in ]?2. Purple and long which in the first case were coupled now showed repulsion. Actual results obtained were Purple long Purple round Red long Red round 226 95 97 1 These is approximately a ratio of 129 purple long; 63 purple round; 63 red long and 1 red round.

Linkage. Prom the seventeen character pairs listed above by Punnett and Bateson, these investigators have definitely detected five linkage groups and publish the evidence for these in Journal of Genetics, Vol. XIII No. 1, March, 1923. (Linkage in the Sweet Pea, Lathyrus odoratus by R.C. Punnett) (A) Under this letter are collected three pairs of characters. Purple - red A 1, long-round pollen A 2 and erect-hooded standard A 3« The linkage between A 1 and A 3 is very close, there being only about 1% of crossovers. The linkage between a * and a 2 shows about 12$ of crossovers. It is probable that the locus of a * is near a 3 and between that of a 2 and a 3* (B) In this chromosome are also 3 pairs dark and light axil B 1; fertile and sterile anther pair B 2; and normal and cretin pair B 3. It is probable that B 2 and B 3 are about 25 units apart while B ! lies about 6 units from B 2 "between B 2 and B 3. Evidence also indicates that the purple maroon pair is found in this chromosome also hut the numhers are insufficient to fix its value or to show the position of maroon in the B chromosome. When a maroon with light axil was crossed with R white carrying purple and dark axil P 1 was dark axilled purple and the F 2 generation consisted of Purple dark axil 99 " light axil 19 Maroon dark axil 9 M light axil 28 White 48 D - This group contains 2 factors. Tendril - acacia D 1 and "bright - dull flower D 2. The number of crossovers 1 is about 33$t placing the factors 33 units apart in the chromosome. P - This group contains 3 factors. Color - R white F •*•; procumbent - Bush F 2 and Self colored marbled P 3. Marbled X R white has always given a marbled P 1 even when the R white used came from a family in which all the colored members were self colored. Self colored plants that throw R whites do not throw marbled while those that give marbled do not give any R whites. R white and marbled must therefore occupy the same locus. There is also evidence of linkage between R white and bush. While bush sweet peas crossed with white procumbent cupids, P 1 was tall purple. P ^ consisted of colored procumbent 130 " bush 53 White procumbent 89 • bush 24

The cross was of the nature g L P L t d (bush) X G x f x P cupid. 25

On a simple trihybrid ratio of 27:9:24:4 we would expect Colored procumbent; colored bush; white procumbent; white bush. Expectation 124 41 HO l8 Results 130 53 89 24 There is an increase of bush plants among the colored and a deficiency among the whites indicating a crossover of 25#« The S 3 generation of 4 families from the above showed the same peculiar distribution of factors. Colored Colored White White procumbent Bush procumbent bush #133 83 57 101 #135 161 70 141 36 42 9 #139 66 26 60 9 #159 21 57In another group of four F 3 families of the ratio 3*1 the results were Colored p Colored White White procumbent Bush procumbent Bush #128 29 8 6 3 #129 20 3 2 2 #158 48 17 1 #l6l 174 66 69 6 #123 and #129 indicate a normal 9:3:3:1 ratio- #158 and #l6l show an excess of bush plants among the colored and a deficiency among the whites, indicating again linkage between bush and R white. 0 - The evidence . points to a linkage between Color - C white 6 1 and purple red purple G 2 with a probable crossover value of 2$%. A red purple was crossed with a strain of C white known to be homozygous for normal ' purple 3? 1 plants were normal purples. The I" 2 generation was raised from 14 similarly bred W 1 plants. In respect of the two pairs Gix and G 2 the distribution was Purple 156 red purple 78 White 80 26.

The red purple class was halfl the size of the normal purple class. This data is insufficient to draw conclusions but Prof. Punnett gives as additional evidence the fact that red purple showB a duskiness that is absent from normal purple. Also the foliage is of darker green and smaller habit. Some of the whites in the P 2 generation showed these habits. This gives us five linkage groups A. B. D. 3?. G. There may be a low grade of linkage between A and C with a crossover of 3^ but the data is insufficient to draw con­ clusions and the evidence rather points against linkage than for it. There would not appear to be any linkage between any of the other factors so that we have at present eight groups. The haploid number of chromosomes in Lathyrus was definitely established by Winge to be seven. # In summarizing his results Prof. Punnett says ## "although the number of apparently independent groups at present stands at 8, the data available are not in all cases sufficient to preclude the possibility of a low grade of linkage between certain of them. Some of these I expect to test further in the near future; and I have also started experiments with other characters which I hope to work into the general scheme. Some years must, however, elapse before I can accumulate the necessary data and I feel that the present juncture is a convenient one for taking stock of the position. < I have come to the opinion that the number of linkage groups in Lathyrus will eventually be found to correspond to the haploid number of chromosomes."

# On the relation between number of Chromosomes and number of types in Lathyrus, Journal of Genetics, Vol. VIII. 1919*

## Linkage in the Sweet Pea Lathyrus odoratus, R.C. Punnett* Journal of Genetics, Vol. XIII. No. 1, March, 1923. 27-

SLOWER COLOR IN SWEET PEAS.

In the original sweet pea, the standard was reddish purple and the wings light bluish purple. The first mutation was the appearance of a white variety. Shortly after this, the Painted Lady having a red standard instead of purple, appeared. Then followed scarlet and then a so called black which was really a very dark purple. These mutations or changes are explained as follows: The original sweet pea possessed five factors• A color base R A color developer C A purple factor B A light wing factor L A factor for intense color I R and C were complementary factors which together produced Red. The purple factor B is a dominant character which modifies the color red to purple. The appearance of the white variety is explained by the loss of either C or R in the absence of which the color red would not appear and hence the modifying factor could not affect it. The Painted Lady or change from purple to red was probably independent of the other mutation and due to the loss of the purple factor B. The loss of the light wing factor from the Painted Lady would ohange the bicolor into one color and intensifying of this color produced the scarlet. Similarly the loss of the light wing factor from the purple bicolor would produce a purple and intensifying of this color into very dark purple produced the so called black. When later on a striped variety appeared, it may have been due to a factor mutation in the purple. The so called "yellow" is certainly due to a mutation in the white and not in the red as might be expeoted. Plants with yellowish coloring have often been observed in white cultures never in reds. The genetic origin of the blue variety » listed in 1806 is not known. Later on about 1840, this blue produced a pea with dark bluish purple standard and pale blue wings. About 1865 the latter, through the loss of the factor for intense color, produced the Blue edged picotee. 28.

It is now possible to express "by the same simple method the relation of the modern shades of purples, reds, "blues, pinks, of hooded and wavy standards. Recent evidence of a chemical nature indicates that the color is due to the interaction of two definite substances. # (l) A colorless chromogen or color base and (2).a ferment which by oxidation produces a colored substance. There must first of all be a glucoside. Further there must be an enzyme which splits this glucoside into chromogene and sugar. The chromogens then gives with an oxydase an anthocyane color; if an x oxydase is active ant,Yt,y x anthocyane will be formed and if a y/Jln'th6<5yanS; eacTT euccessive oxydation through a specific oxydase will give a darker colored tinge. There sometimes is an inhibiting factor which prevents the oxydase from becoming active and thus prevents coloring, (produces whites) The main causes for formation or prevention of color can be expressed according to Miss Schiemann in the two formulas: A GlucoBide f H_ 0 + glucoside splitting enzyme = Chromogen and sugar. B Chromogene +02+ oxydase = Anthocyane. Those chromogenes which are solved in the cell sap (not the plastic pigments like chlorophyll, etc.) are divided up into yellow pigments, soluble in ether (called Anthoxanthine) and into blue-violet-red pigments soluble in alcohol but not in ether (called anthocyanine) by Wills- tatter. So far there has been no sweet pea discovered which contained these yellow pigments. The anthocyanine blue is dominant in sweet peas over red. Prof. J. W. Crow, in Improvement of Ornamental Plants, says ## "Red color in flowers is known to be associated with acid conditions" The uneven or irregular application of lime may account for the spotting on certain red varieties or those containing red sap.

# Breeding Sweet Peas, by W. Newton, Berkeley, California, 1923-

## Canadian Florist, Nov. 6 and Nov. 20th. 1924. 29.

ROGUES IN SWEET PEAS. Major C.C. Hurst, E.L. S., Superintendent of the National Sweet Pea Society's Trials in 1911, reporting to the annual meeting of the N.S.P.S. # defined rogues a6 follows. A "type rogue" is a plant hearing flowers which are not of the true "Spencer" type. The true Spencer type has large flowers (except in some salmon and scarlet shades) with the standard and wings waved or frilled and an open keel. The open keel is the hall mark of the true Spencer. In the old - so called "grandiflora" - type the keel is closed, the stamens and pistil "being closely clamped together at the apex causing the pollen to shed within the keel and the pistil to protrude. Type rogues are of course variable in other respects; some have hooded standards while in others the standards are erect, others again have slightly waved standards while in most the standards are quite plain. All, however, resemble one another in having clamped keels. Experiments carried out at Burbage Experimental Station show that the clamped keel "behaves as a Bingle Mendelian character dominant to the open keel of the Spencer type which is recessive. Consequently, if seed be carefully saved from plants with open keels only and all clamped keels are eliminated from the seed grounds, no type rogues should appear at all in our sweet pea cultures. In view, however, of the known "behavior of certain recessive cream and white sweet peas, which when crossed may give rise to dominant Red and Purple colors, (due to the bringing together of complementary factors) the possibility of a dominant "type rogue" arising from an outside cross between two recessive Spencers, must not "be overlooked "but so far there is no evidence of the occurence of such a thing and the possibility seems rather remote as from 43 plants growing together uncovered, not a single type rogue occurred in 8840 plants, although some cross fertiliz­ ation did take place. The practical advantage of realising that the type rogue is a Mendelian dominant is that no matter how mixed in type a certain stock may "be, if the dominants are rogued out properly, the stock will "breed perfectly true to recessive Spencer type.

# Sweet Pea Annual, 1913, Page 21. Report of 4th. Sweet Pea Conference. 30.

There will consequently "be no need to discard such a stock "because it is mixed in type nor will there be any need to attempt to refix it from single plants. The whole stock can he safely utilised for seed provided that the dominant type rogues he all eliminated from the crop as soon as they appear. Color rogues may he conveniently divided into two classes. Dominant (epistatic) and Recessive (hypostatic) Dominant color rogues are those whose color characters are known to he dominant to the color characters of the parent stock; that is to say their color is due to the presence of a higher factor or factors added to those present in the parent stock. Recessive color rogues are those whose color characters are known to he recessive to the color characters of the parent stock; that is to say their color is due to the absence of a higher factor or factors present in the parent stock. From Mendelian experiments with various colors of Sweet Peas at Cambridge and Burbage, sweet pea colors have been classed into dominants and recessives as follows. Cream is the lowest recessive color. Tinged white is dominant to white. Orange and salmon are dominant to Tinged White. Pink is dominant to Orange and Salmon. Crimson is dominant to Pink. Deep and pale blue are dominant to Crimson and Reds. Lavender is dominant to deep and pale blue. Mauve is dominant to Lavender. Maroon is dominant to Mauve. Purple Maroon is dominant to Maroon. The Wild Purple Eicolor is dominant to all other colors. In Color Patterns. Light wing bicolors are dominant to dark winged selfs. Selfs are dominant to picotees. Selfs are dominant to marbling. Selfs are dominant to striped and flakes. Recessive Color Rogues. Recessive Color Rogues may be expected in any heterozygous or unfixed stock. In the commercial stocks tested at Burbage in 1911 in the deep cream-pink and the deep pink sections, no less than 78 recessive "color rogues" appear in 483 plants. The majority of these can be traced to 31.

certain well known heterozygous varieties "Miriam Beaver" "Syeira Lee" and"Audrey Crier". Experiments at Burbage show that these varieties are permanently heterozygous and quite unfixable the deep cream pink shade being the F l hybrid between a pale cream pink and an orange pink. These can never breed true but will always throw the light and dark forms on the average one-quarter of each. The light and dark colors will, of course, breed true and the middle or hybrid form can always be obtained by crossing the light and dark colors together. Recessive color rogues may also arise from accidental mixture or accidental cross fertilization. While dominant color rogues will always appear the first year, after the accidental crossing takes place, the recessive rogues will not appear until the second year after cross fertilization.

Dominant Color Rogues* Dominant color rogues can be explained in two ways. First, faulty roguing of seed plots and secondly, cross fertilization. The former is due to carelessness and does not concern this article. The second is most interest­ ing and useful to a seed grower. In the stocks grown from commercial seed in the test plots at Burbage in 1912, a number of dominant color rogues, chiefly maroon, mauve, and rose bicolors, all with red axils were found in the cream variety "Clara Curtis". These are of peculiar interest for their presence was not due either to faulty roguing or accidental mixture because colors in the cream stock came from seeds with light colored skins proving that they were gathered from either a cream or white mother plant. The fair presumption is that they were gathered from Clara Curtis plants. If they had been gathered from purple or red rogues or were accidental mixtures, they would certainly have come from dark colored seeds. A similar case appeared in the National trials where an unnamed cream stock produced dominant red rogues with red axils from seeds with light colored skins. As previously shown, red color in sweet peas is due to the simultaneous presence of two complementary color factors known as C and R while purple color is due to the addition" of a third factor B. A cream sweet pea lacks either C or R or both, while B may be present or absent. A self fertil­ ized cream plant can give creams only and the only way a purple or red rogue can be produced from a cream plant ie by 32. the introduction of a second oolor factor by cross fertilization. It is evident that all dominant purple and red rogues coming from light colored seeds in cream stocks are due to cross fertilization. It may he interesting to record the positions occupied by the mother plants that threw the dominant rogues and their minimum distances from plants of other colors* 5l E (Thomas Stevenson, orange scarlet) was only 4 feet distant from the nearest orange pink plant while 98 A (Edna Unwin, orange scarlet) was no less than 104 yards distant from the nearest plant carrying the blue factor, yet it threw 48 dark mauve rogues in 2o6 plants- It was the last plant of the last row of a plot and was the most accessible plant to an insect visitor coming from the plot where the blue saps were growing.

It would appear that the pollen was conveyed by an insect of considerable flying power and to a single plant only while in the other cases the distance to be traversed was short and several adjacent plants were con­ taminated so that possibly ground insects might be the culprits. It has been stated on good authority that all sweet peas grown in Sicily or Maderia revert back to the wild purple. As the sweet pea is a native of Sicily, it 1B probable that pollen of the wild species (which is dominant over all) is conveyed to the flowers by some native insect. The following table gives the summary of rogues found in one Cowichan seed grower's crop in 1924. Where the plant had a wrong axil it was classed as a type rogue and no record was kept of its color. In making the summary of color rogues, wrong shades of color were classed aB doubtful. It is quite probable many of these were not rogues at all but the slight variation in color was due to physiological conditions such as sun burning. These results show that sometimes stock seed supplied by British seed houses is not absolutely true. There is not much excuse for the dominant color rogues appearing in certain varieties, for example daffodil. The dominant color rogues were strangely enough, nearly double the number of recessive color rogues found. M u o • H o H T» t> rS O 41 4) 4) M O o U P, M -»-» O •H 1 O-H u -r-» m £ rH TJ 3 4) 0) m CO tJ +> 4> c V fH •d C 4) t) 4> CO M 0> o A 00 3 o c 4> O rH +» rH u> H Variety. 1 4) a I o Tl £ 3 U •a o 3 > 3 se & 4* aJ 4> •H •H a) as T* o O O g CQ O 12 ^ ^ 1*

Daffodil, cream 20 3 49 18 2 6 6 i 1 Matchless, cream 2 3 1 1 Maecot'e White # l Bunty, Orange pink 8 2 2 2 1 2 Lucifer 14 2 2 Royal Sovereign, orange 1 176 Tangerine, orange 3 1 1 1 4 President Harding l 2 8 Picture, cream pink 3 19 2 1 47 Doris, pale cerise 1 17 l 2 7 2 2 Hawlmark Pink 2 1 9 Mary Hose, rose 1 5 1 3 1 Gloriosa, orange scarlet l 3 4 Hawlmark Scarlet, " 3 1 Mascot's Ingman, " 4 12 2 i 5 6 Royal Scot, scarlet 3 2 8 Gladys, lilac lavender 6 4 l 3 2 1 2 4 21 19 Powerscourt,M " 4 4 2 7 3 6 10 25 The Sultan, maroon 1 1 Mascot's Purple 33 133 4 6 6 10 3 3 12 5 u ^ O • o H T> iH O 43 4> O o t3 ^ » o •ri M oq § n •> 4) C » *« TJ C c 4) 41 CO rH «-t tt> rS Variety. B c3-pgt8-H,M4J«>aSa;>o *-> c S* & o (0 O03-rlp-jSlhs:o^M>3M v4 M O a &=ogcQaqoa.d(Pq^-l^aa £ *1 s St

Clara Curtis, cream 1 8 1 12 White Spencer, " # 2 11 Giant Attraction,pink 7 2 5 l6 15 Mascot*s Ingman 2 19 11 2262 20 Hawlmark Lavender 10 11 1 1 5 8 7 69 RavenfE Wing 8 1 3 1 3 The Sultan, Maroon 1 1 Le Mahdi, purple 3 38 1 l8 1 2 76

The majority of Mascot's White have clamped keels. They have, therefore not teen rogued out. Entries under wrong shade may, in part be discoloration of flower, caused by hot sun or heavy dew but were rogued out for precaution. White Spencer also showed a very great percentage of clamped keels and were not rogued out. Upper list grown for Hurst. Lower list grown for Carter & Co.

k 35-

SUMMARY OF ROGUES. y w H 0 O) 0 0 a 0 c*- c+ % W « W • p ' 9> V! 0 H H Variety. ID 0 0 l-» M 0 0 O n> O H 1 w> O O V- a d H 4 O o>- • M o 4

Daffodil 20 20 85 85 105 9.7 Matchless 2 3 2 2 7 0.5 Mascot* s White # I 1 1 Bunty 8 8 7 2 9 1.4 Lucifer 14 14 4 4 iS 1.5 Royal Sovereign 0 0 0 176 1 0 177 13-4 Tangerine 3 3 6 1 7 10 0.6 President Harding l l 10 10 11 1.0 Picture 0 47 3 22 72 72 7.0 Doris 1 17 2 9 3 14 32 2.2 Hawlmark Pink 2 2 9 1 10 12 1.0 Mary Rose 1 1 1 9 10 11 1.0 Glorioea 0 4 3 1 8 8 0.7 Hawlmakr Scarlet 0 1 0 3 4 4 0.3 Mascot * s Ingman 4 12 16 6 6 2 14 30 2.4 Royal Scot 3 3 10 10 }3 0.9 Gladys 6 4 10 21 25 7 53 £3 4.5 Powerscourt 4 4 8 25 16 12 53 61 2.4 The Sultan 0 1 l 1 0 1 2 0.2 Mascot's Purple 33 133 171 5 12 32 49 220 15.2

Clara Curtis l 8 9 4 4 13 0.4 White Spencer # # 2 2 4 Giant Attraction 7 2 9 31 5 36 45 1-9 Mascot's Ingman 2 19 21 20 12 2 34 55 2.1 Hawlmark Lavender 10 11 21 74 15 2 92 113 4.0 Raven's Wing 0 8 8 3 4 1 8 16 0.9 The Sultan 0 0 1 1 0 2 2 0.1 Le Mahdi 3 38 41 76 2 20 98 139 5.6

The majority of Mascot's White have clamped keels. Entries under wrong shade may in part be discoloration of flower caused by hot sun or heavy dew, but were rogued out for precaution. White Spencer also showed a very great per­ centage of clamped keels, not rogued out. 36

AXIL COLORATION IN SWEET PEAS.

At a meeting of the Scientific Committee of the Royal Horticultural Society, held on May 1st., 1906, Wm. Cuthbertson, J. P., F.R.H.S., drew attention to the variation in the color of tendrils and asked if anyone had ascertained the significance of these variations in color. At the next meeting of this Society on May 15th., of the same year, a communication from Mr. Bateson, E. R. S. (Cambridge University) was read in which he said "We have kept note of this character as far as possible in our work- The red tendrils are (? always) associated with red in the axils of the leaves. In our records we have Epoken of this feature as 'dark axil1 the opposite as 'light axil'. The •dark axil* character may be present in any sweet pea, whether the flowers are colored or white but it is not developed unless the flower is in some degree colored, we believe. There are whites with dark axils, e.g. the black seeded form of Mrs. Sankey but we think the whitest of such flowers always have a trace of color in the keel. At all events there is no dark axil plant which does not have a black seed coat. Those who grow Sweet Peas under glass at the beginning of the season will find when the plants are about four inches high, they produce tendrils of consider­ able size. These are colored or green according to the variety."

Early in the summer of 1906, Mr. Cuthbertson together with Mr. E.J. Chittenden, Hon. Secretary of the R.H.S. Scientific Committee, marked a few unbloomed plants whose tendrils varied from those of their neighbors. Amongst them in a line of Captain of the Blues, one plant which had green tendrils was marked. All others had red or brown tendrils. When the marked plant bloomed, it was Captain of the Blues in form and character but the flower was white marbled with blue. This was characteristic of others marked. A loss of color in the tendrils was followed by a loss of color in the flower. He further pointed out that these plants were fully as vigorous and healthy as their neighbors. Mr. Cuthbertson continued to observe this character closely and in the 1915 Sweet Pea Annual, he published a table (checked by Andrew Ireland in Essex and Mr. James B. Macfie of Dobbie & Co., Edingurgh) giving the axil colors of some 68 varieties. In commenting upon this table, he says he is unable to present a working theory to explain the variation. 37-

Maroons, crimsons, scarlets, "blues, purples, have all light axils without exception whereas all the mauves have dark axils. All the white ground pinks includ­ ing the original waved variety Countess Spencer, have dark axils. The cream pinks do not follow a definite rule. Two outstanding varieties have light axils. Mrs. Cuthbertson a white ground pink "bicolor has dark axils while Mrs. Ireland, a cream ground "bicolor, haB light axilB. All the 'edged' class have light axils, although Elsie Herbert might "be expected to have dark ones. The salmon, orange, cerise, rose and carmine are all light axil.

_ In P the dark axil is dominant to light axil. In P the characters segregate along Mendelian lines.

COLORS OF AXILS IN SWEET PEAS. White Colored Varieties.

Light Axil Dark Axil # Etta Dyke Constance Hint on, D. S. # King White # Nora Unwin # Edna May Edna May Improved Joan Ryder Mascot's White Moneymaker White Perfection White Spencer White Treasure Ivolanek's White Snowstorm

LIGHT LAVENDER LILAC & LILAC LAVENDER. Light Axil Dark Axil # Dohbie's True Lavender # Aldred Watkins # Quaker Maid Gladys King's Lavender (dark) Powersoourt Lord LaBcelles Burpee's Lilac Pink 38.

DARK LAVENDER. Light Dark

# Lavender George Herbert # R. P. Pelt on # Ivanhoe Austin Frederick Imp, Mrs. Chas. Zvolanek

CERISE ROSE CARMINE. Light Dark # Illuminator Sunset (rose) (N.B.) # J. Ingman Rosemary (N.B.) # Norma # Rosabelle # Ruby Palmer # Decorator # Edith Taylor Mascott's Ingman Doris Glory Hawlmark Cerise Brilliant Charming Alex Malcolm Royal Scot Wonderful Bacchus (wine) Honor Bright Eiery Cross Kenn eth (ro se) Renown Royal Cherry Royal Sovereign Lucifer Hope (Rose) Mary Rose (See pink cream^ Rosy Morn ivolanek's Beauty (rose) (dark) Rosebud (dark) Torch (dark) Rosalind (dark) * 39-

PINKS WITH WHITE GROUND.

Light Dark # Helen Lewis Rogue Audrey Crier N B. in Audrey Crier Princess Victoria rogue in Audrey Crier NB. Antonio Dolored Dobhie'e Prilled Pink Countess Spencer Felicity Elfrida Pearson Songoird (dark) Princess Victoria Hercules Elegance Conquest (Flushed) Dark Fairie Queen (Flushed) Advance (light) Dai sybud Mrs. Chas. W. Unwin

PINKS WITH CREAM GROUND. Light Dark # Duplex # Mrs. Hugh Dickson # Mrs. Roulzahn Giant Attraction # Doris Usher Beryl # Lady Millar Mary Rose (of cerise) # Margaret Atlee Rose Queen # Duchess of Portland Daybreak # Mrs. Hugh Dickson Fairy Lady ^rs. Arnold Hitchcock Picture W«r J. Unwin C. W. Unwin Hebe Hawlmark Salmon Pink Comrade Dignity Fairie Queen Hercules Hawlmark Pink (trace) Margaret Atlee Ringdove 40.

FANCY Light Dark # Chas. Foster # Prince George MAUVE Light Dark # Mauve Queen # Bert rand Deal # Mrs. Mcllurick # New Marquis # Queen of Norway King Mauve Shamrock

LIGHT BICOLOR & DARK. Light Dark Mrs. Anne Ireland (dark) Mrs. Cuthbertson (light) Dora Bonfire (light) Adelaide (dark) Zvolanek's Xraas. Pink Yarrawa (dark) Orchid (light) Columbia pink and white bicolor (dark)

CREAM FLOWERED VARIETIES. Li£ht Dark # Dobbie'e Cream # Isobel Malcolm # Clara Curtis # Lady Knox Majestic buff edge Matchless Daffodil Champagne Golden Orchid 41.

PURPLE _ Light Bark # Royal Purple # Marks Tey # Menie Christie Le Mahdi MaBcott's Purple Purple Perfection

BLUB Light Bark # Mre. George Charles # Flora Norton Spencer # Princess Mary Mrs. Tom Jones Colne Valley (light blue) Coinsander Godsall (dark blue) Jack Corn well V. C. (dark blue) Bluebird (dark)

MARDOB Light Bark # King Manoel # Nubian # Mrs. Cowdy Hawlmark Maroon Splendour Bavenswing Warrior The Sultan

STRIPED light Bark. Senator Spencer # Loyalty # May Campbell # May Carmine Rouge 42.

SALMON AMD ORANGE. Light Dark # Edrom Beauty # Inspector # Melba # Thos. Stevenson # Dobbie's Orange Royal Sovereign (0) Tangerine Imp. (0) Wizard (o) Bunty Geo. Shawyer Gloriosa May CowdyB Barbara Edward Cowdy Fordhook Orange Liberty President Harding Royal Flame Zvolanek's Orange Illuminator Glitter Flamingo Poppy

EDGED Light Dark # Jean Ireland # Mrs. C.W. Breadmore # Elsie Herbert # Blue Picotee Youth Annie Ireland (see bicolor) The Fairy 43-

CRIMSON & SCARLET. Light Dark # Sunproof Crimson Scarlet Duplex # Dobbie' s Scarl et # Red Star Charity Field Marshall Hawlmark Scarlet Mascott's Scarlet Mrs. C.P. Tomlin Maud Holmes Crimson King Grenadier

# Varieties marked # described "by Cuthberteon.

In many of these varieties, a reddish coloration may be observed in the axils of the leaves. The amount of color varies with different varieties. Some have no color at all, others have a slight color in the axils only, while in others the color appears on the flower stalk, tendrils, mid rib veins and margin of the leaf, in lines along the stem and even in the little hairs on the stem. This color may he observed after the plant appears about ground and to the experienced grower this is a valuable aid in roguing. Curiously enough, when the sweet peas are started in the greenhouse, this coloration is not apparent. The plants, however, develop the color when transplanted to field conditions. Why thiB occurs offers an interesting subjedt for study. . INHERITANCE IN SWEET PEAS. Experiment 1.

Theory-> The first double sweet pea was Bride of Niagara, a double strain of Blanch Fairy, or its Prototype introduced in 1896 "by James Vick & Sons. Prof. R.E. Clausen, Department of Genetics, College of Agriculture, Berkeley, says "As to the Duplex •iiaracter it is certainly inherited because it appears only in certain varieties. It is not, however, uniformly expressed in a plant. If different plants of a sowing show a significant difference in its expression, it should "be possible to improve the variety in this respect by selection. If not, it may still be possible to increase the proportion of Duplex flowers by crossing to some un­ related strain and selecting in F 2 and subsequent genera­ tions* I believe some of the sweet pea breeders are giving a good deal of attention to this matter."

G. W. Kerr, Seedsman to W. Atlee Burpee Co., Philadelphia, says "Practically all Spencer varieties when well grown, do at times throw duplex flowers and I have never put it down as having anything to do with Mendelism. Some varieties produce more double flowers than otherB with the result that several duplex varieties have, at various times, been introduced, but to retain this form, seeds should always be saved from double or duplex flowers and as that type of flower seeds very shyly, it is always difficult to get a good crop. You may note, however, during the season, that where the first flowers on some plants were single or double, they begin to throw the true duplex blooms as the plants get into their full stride and at the height of their blooming. One of the most duplex forms I know was introduced into England this year under the name of 'Kenneth'. When the plants first bloomed in the spring, they only gave slight indication of doubling but within ten days afterwards, practically every bloom was duplex". Miss Saunders* work with single and double stocks suggests strongly that ovules and pollen grain of the same plant may differ in their transmitting properties, probably owing to some process of segregation in the growing plant which leads to an unequal distribution of some or other factors to the cells which give rise to the * ovules as compared with those from which the pollen grains eventually spring. *5-

Objects of Experiment 1. (a) Starting with a strain known to possess the character of throwing numerous duplex "blooms, to endeavor to isolate pure single throwing, and duplex throwing strains, and if possible "by crossing these to study the relation of trans­ mitting powers. (b) To study the relation of the duplex character to the production of seed and its consequent effect on the seed industry. (c) To ascertain the relation of duplex character to different stages in the growth of the plant and its con­ sequent relation to roguing. (d) To ascertain the effect of heavy fertilization on the number of duplex blooms produced. (e) To study the relation of the moisture supply to the production of duplex characters.

Experiment. Plant sufficient seeds of the scarlet duplex variety in flats to produce 120 plants for transplanting. Plant these out in six rows to be later named A B C D E P. Set plants 24 inches apart in the rows and rows also 24 inches apart. (a) Prom A remove all single blooms as soon as they open, leaving only duplex flowers to mature and produce seed. (b) Prom B remove all duplex blooms leaving anly single blooms to produce seed. (c) Leave C as a check row. (d) Select plants purely single; plantB purely duplex; and plants showing both characters. Select seed pods from these plants for comparison with pods from A and from B. Plant these out the next season to ascertain their nature. (e) Heavily fertilize row E with a complete commercial fertilizer. (f) Water one half of P regularly and freely with a hose. Do not water the other half at all or very sparingly. 46.

Observations to be Made and Points to be Recorded with Exp. 1.

(a) Number each plant in each row, for example, A 1, B £, C 7, etc (b) Record the date of the first bloom on each plant and the nature of the bloom. (c) Make daily records of each plant for the first ten days after it blooms showing the number of single and of duplex blooms on each plant as in the form below. 12 34-56 789 10 ROW. S.D. S.J). S.D. S.D. S.D. S.D. S.D. S.D. S.D. S.D.

A 1

A 2 -

B 5 ETC

(d) Collect 100 pods from each of rows A, B, C, D, E, and F. Shell these out individually and calculate the average number of peas per pod grown under the different con­ ditions. (e) Select seeds from the individual plants for planting out next year putting these seeds in envelopes and mark on each the following data:

Plant Ho. Row Nature of Bloom Date gathered No. of Seeds in Pod — 47.

Observations.

1. 24 inches x 24 inches is too close planting. 36 inches x 36 inches recommended for similar conditions. 2. The method of recording the number of "blooms is defective. It was simple enough to remove all singles from Row A or duplex from Row B and record the numoer of these hut after the third day it was impossible to record the true number of blooms remaining on the plant. Some blooms set, others dropped without setting. Some blooms would be counted on two or three successive days. The total number of blooms left on each plant in Row A OK. removal of single blooms was recorded daily. Similarly with Row B. 3« No plants were found to be pure single or pure duplex, therefore row four was useless. 4. A "Complete" commercial fertilizer was used and in Row J> where applied heavily, killed a number of plants by coining into direct contact with the tender young plant. Results from this test were inconclusive. J>. No difference could be observed in development of duplex blooms due to watering freely. 6. The small number of seeds per pod with this variety, shows that commercial growers cannot afford to rogue all single blooms from so called duplex varieties where ordinary stock seed is supplied, unless the price paid per pound of seed is greatly increased. 7« Many of the duplex blooms were So badly deformed they failed to set any seed even under ideal weather con­ ditions. 8. Some plants showed a greater tendency to produce duplex blooms than others. Seed from these will be tested out for further tests. 9- Some plants did show a greater tendency to throw duplex blooms as the season advanced. 10. Numerous stems were found carrying both duplex and single blooms. , SEED PODS COLLECTED FROM SCARLET DUPLEX.

Row 1, all einglee removed. Plant; Bloome See ds in each Total Ave. Single - Double pod seeds seeds in pod

A 13 3 Small plant, only 3 duplex flowers. None seeded. B 1 8 Died 1earl y in the summer.

C 137 90 1 1 D 113 134 1. Pulled "by accident Aug. 12th. 1 1 E 6o 22 2 2 2

7 Blank G Blank H 2^4 53 1, 1. 1, 8 11 2.75 I 189 118 3, 1, 8, 1, 5, 1,7, 26 3.73 J 143 105 2, 1, 1, 4 1-33 K 88 106 1, 3, l, 5 1.66 L 10 11

M 156 109 2, 1, 3, 1, 1, l, 1, 10 1.43 N

0 210 134 1, 1, 2 1.

29 - 62 2.13 49-

SINGLES, All duplex blooms removed.

^lante Blooms Seeds in each Total Ave. Singles-Double pod . Seeds Seeds in pod A B 181 3 4 2. C 153 29 2, 1, 3. 1, 1, 8 1.60 D 137 0 E 8 2 Died early in the season. F 71 9 Died early in the season> G 141 15 1. 3, 9. 6, 8, 3, 3, 40 4.44 5, 2, H 182 6 3. 6, 4, 3, 4, *. 5. 3, 32 4.0 I Blank J 268 7 3, 3, 2, 1. 6, 15 3.0 K 226 30 1, 1, 2, 4, 3, 3, 14 2-33 L Blank M Rogued N 178 28 1, 2, 4, 2, 1. 8, 1. 1, 1. 21 2.33 0 83 8 4, 1, 1, 4, 3,4, 1, 7, 5, 2, 3,7, 43 3.30 P 106 16 3, 3, 1, 3, 2, 2.66 4, 16

63 193 3-*>6 ?o.

Row 3- Check Row.

Plant Blooms Seeds in each Total Ave. SingleB-Dou"bles pod Seeds Seeds in pod A 141 5 B 44 18 6, 6 C Blank D Blank E 94 12 3, 3, 5, 2, 5, 3, 3. 5, 3, 2, 2, 1, 1, 3, 4, 1, 2, 48 2.82 J Blank G Blank H 125 21 4, 3, 3, 4, 2, 5, 5, 2, 2, 1, 3. 4, 2, 2, 1, 4, 1, 2, 4, 50 2.63 I , Blank J 40 14 1 1 K 59 16 3. 3. 6» 3- L 139 27 3, 1, 4, 6, 2, 2, 3. 3, 3. l. 6, 2, 2, 1, 1, 1, 4, 3, 3, 51 2.68 M 114 22 3, 1. 4. 1, 1» 1. 1, 4, 4, 2, 1, 23 2.09

70 185 2.64 51.

Rpw 4. Selection of Special Individual Plants. Plant Blooms Seeds in each Total Ave. Single-Double pod Seeds Seeds in pod. A 33 6 5, 2, 4, 2, 10, 23 4.60 B 21 0 4, 4 C 28 34 2, 5, 3, 1, 2. 2, 2, 3. 4. 3, 3, 2, 1, 2, 3, 5, 2, 3, 48 2.66

24 75 3-12

Row 5* Heavily Fertilized.

Plant Blooms Seeds in e ach Total Ave. Single-Double pod Seeds Seeds in pod. A 26 4 6, 4, 7, 4, 3, 24 4.80 B Blank C 39 18 3, 3, 3, 4, 5, 3, 2, 1, 2, 3, i, 2, 2, 2, l, 4, 2, 4-3 2-53 D Blank E 24 6 5. 6, 3, 5. 3. 2, 2, 1, 3, 2, 32 3.20 F 61 18 7, 2, 3, 3, 2, 4, 3, 3. 5, 2, 4, 38 3.45 G 41 9 2, 2, l, 1, 7, 4, l, 5, 5, 3, 3, 3. 4, 2, 43 3.07

57 180 3*15 52.

Row 6. Plants A to H watered freely. I to 0 watered sparingly. Plant Blooms Seeds in Each Total Ave. Single-Double pod Seeds Seeds in pod

A 44 19 2, 5, 1, 2, 4, 4, 2, 2, 3. 2, 5, 1, 2, 35 2.69 B 18 3 5, l, 1, 2, 4, 4, 6, 7, 5, 3. 5, 2, 2, 5, 3, 55 3.66 C Blank

D 18 6 5, 4, 3, io: 1 22 5.50 E Blank F 44 l 5, 2, 5, 2, 2, 3, 5, 4, 28 3.50

G 32 10 3, 1. 2, 2, 3, 5, 7, 1. 1, 2, * 46 3.28 H Blank I 75 0 3, 4, 6, 8, 2, 5, 4, 5, 37 4.62 J 18 3 3, l. 3, 2, 9 2.25 K 3 l 1. 2, 2, 4, 3. 4, 3, 4, 2, 1. 26 2.60 L 30 15 l. 2, 6, 4, 3, 2, l, 7. 1, 2, 1. 2, 32 2.66 If 10 12 1, 3, 1. 5 1.66 N 8 5 2, 4, 5, 6, 2, 2, 2, 23 3.28 0 35 l 2, 1. 3 1-5

100 321 3-21 53-

SUMMARY.

(l) Careless or inefficient roguing of seed plots seriously imperilled the market in Britain for Canadian growers. These studies were commenced to assist the growers in roguing. {2 The sweet pea, a native of Sicily, was brought to England in 1699.

(3 Improvements were made by selection and natural breaks until cross fertilization was begun in 1883. (4 The discovery of Spencer type in 1900 marked a crisis in the development of the flower. (5 Sweet peas offer numerous illustrations of genetic principles as presence and absence theory, interaction of factors, complementary factors, reversion, mutation, linkage and crossing over. (6 All color in sweet peas is due to presence of two complementary factors. (7 Five linkage groups definitely established with the possibility of a low grade of linkage in other characters suggests that the linkage groups will correspond, to the haploid number (7) of chromosomes. (8 Rogues are of two kinds (a) type; (b) color. (9 Ability to distinguish type rogues is a vital necessity in roguing. Color rogues are of two classes, dominant and recessive. (10 The former indicate either that the roguing haB been faulty or else that cross fertilization has taken place. The order of dominance in color is a valuable asset to (11 the grower. (12 The variation in the color of axil in different varieties may be used to good advantage in roguing. SOME SUBJECTS EOR FJRTHER STUDY.

(1) Why do the dark "blue varieties show a thickening and wrinkling of the leaf (giving the appearance of rhizoctonia) in the first few weeks of growth? (2) What causes the change in intensity of color in the picotees, lavenders, &c whereby plants that appear true when they first bloom are far from true to color in their later blooms? Is this condition genetic or physiological? (3) What is the relation between soil acidity and intense color in the red varieties? Do commercial fertilizers affect this color of bloom? Also does lime cause blotching and spotting of color? (4) Why do some varieties started in flats and kept at nozmal air temperature show much coloration in the young plants, while the same varieties in the green­ house show little or no color? (5) I» cross fertilization taking place in British Columbia seed plots? If so, what insects are responsible for this crossing? (6) Is the apparent difference in yield from different varieties taken into consideration in setting prices for seed growing contracts? INDEX.

Atavism 8 Axil Coloration 36 - *3 Character Pairs in Sweet Peas 15 Chromosome Theory 10 Complementary factors 8 Coupling 22 Cretin 15 Cross Fertilization (early) 4 Crossing Over 12 Cupid 5 Dihybrid Ratio 9 Diploid Number 10 Dominant Color Rogues 31 Duplex,Experiment with 44 - 52 Duplex, Nature of 44 Early Improvements 3 Early Types 3 Factor 7 Flower Color in Sweet Peas 27 Genetic Terms Haploid Number History and Development 3 Interaction of Factors 8 .- 18

Linkage 11 -• 23 Locus 11 Mendelian Ratios Monohyhrid Ratio Mutation Order of Dominance 30 Presence & Absence Theory 7 Recessive Color Rogues 3° Repulsion 22 Reversion 8 Reversion with 2 Factors 20 Reversion with 3 Factors 21 Rogues in Sweet Peas 3° Spencer Type 4 Telemy 5 Trihybrid Ratio 9 Triple Heterozygotee 9 Unit Character 7 Winterflowering 5 Zygote 7