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The Botany of the Citrus Fruits and Their Wild Relatives As a Guide to Their Use in Breeding

The Botany of the Citrus Fruits and Their Wild Relatives As a Guide to Their Use in Breeding

156 FLORIDA STATE HORTICULTURAL SOCIETY

THE BOTANY OF THE AND THEIR WILD RELATIVES AS A GUIDE TO THEIR USE IN BREEDING

WALTER T. SWINGLE Collaborator9 U. S. Department of Agriculture

Fifty years ago, in April, 1893, I read fungicides in Europe, with salary but with a paper beforethe4th Annual Meeting of no expense money of any kind. 1/ the Florida State Horticultural Society giv By July 1, 1899, the Introduction ing a list of a number of Citrus fruits not Service was established in the Department yet grown in this country, and suggesting of Agriculture by David Fairchild. Both the organizationof a non-profit stock com he and I were commissioned as Agricultural pany to introduce new Citrus fruits from Explorers and sent at once to foreign re the Old World. I expected at best a few gions, he to the East Indies, and I to the words of thanks for my paper and was countries bordering the Mediterranean. From greatly surprised to "see the leading that day to this a stream of Citrus varieties growers of Florida (there were no grape and Citrus wild relatives has been entering growers then)get up, one after an this' country from all the warmer regions other, and give their warm approval to the of the world. project. Finally by a unanimous vote of the Dr. Fairchild, Dr. Webber, Prof. G. W. Society, a committee was appointed to or Groff and I, all members of the Florida State ganize such a Citrusintroduction company. Horticultural Society and the Krome Insti While this committee still had the matter tute, have all of us worked in season and under consideration the two great freezes out to secure new Citrus fruits for this of December, 1894, and February, 1895, country. Having lost during the great freezes killed to the ground all the Citrus trees in of 1894 and '95, all of the many Citrus the commercial groves and it was, of course, hybrids I had made in 1893, I determined impossible to consider going ahead with the to get a Subtropical Station in the. Miami Pensacola project. However, the great interest shown by the 1/ In April, 1899, I made the first suc leading orange growers of Florida convinced cessful shipment of the fig wasp ( Blast o- Dr. Herbert J. TjTebber, Dr. David Fairchild phaga psenes) which breeds in the fruits and me that somehow this work of intro ofthe male fig trees (or caprifigs) and ducing Old World Citrus varieties and wild carries pollen to the young flowers of relatives should be undertaken as soon as the best varieties of figs used for drying. possible, if practicable by the U. S. Per This shipment reached America too late partment of Agriculture if authority could to get established in caprifig trees grow be secured to spend money abroad. ing in Fresno, California, buta ship In 1894 Dr. David Fairchild studied ment I made from Algiers in March, culture in Corsica and introduced into this 1899, arrived in Fresno on time, and country the famous Corsican citron. In 1898 by October 1899 was well established. I sent to Washington from Naples, Italy, This introduction of the fig. wasp made the other important citron variety grown possible the growing in California of in Italy, the Liscio or . This dried figs of the Smyrna type to the ex I did while on my way to work on copper tent of 10-12 thousand tons annually. FLORIDA STATE HORTICULTURAL SOCIETY 1S7 region where young hybrids and delicate Lingnan University, Kwok Wah-Shou, the tropical Citrus relatives could be grown son of a Citrus grower, worked for me un safely. Thanks to the efforts of Mr. Ingra- der the immediate supervision of Prof. G. ham, his chief, Mr. Flagler approved the W. Groff for two years on the varieties of plan, and the Florida East Coast Railway Citrus grown around Canton, China. He de allowed me to select a tract now in the city scribed and figured about one hundred varie of Miami, and it was placed at our disposal. ties, mostly oranges and pummelos. Citrus A legal technicality prevented the U. S. De is grown in almost all the lowlands in the partment of Agriculture from accepting the south' half of China, an area about the size deeds tendered to them and finally this of all of the United States south of the property had to be vacated. Dr. David Fair- Potomac, Ohio, Missouri and Kansas Rivers! child thereupon leased properties north of Citrus trees have been grown in many parts the Miami River, which some years later of China for three or four thousand years had to be given up. Due to the tireless ef and innumerable seedlings have arisen in forts, a permanent Plant Introduction Gar- dooryard or village groves. A few of them den was finally established at Chapman have been proved to be new and superior Field and for many years rare Citrus fruit sorts, some of them complex hybrids made trees and related trees have been growing through cross pollinations effected by bees vigorously there. or other insects. Undoubtedly a thousand Thanks to this succession of Federal Sub or more varieties and strains of Citrus tropical Gardens, to the Florida State Uni fruit trees are now grown in China and versity's Subtropical Station at Homestead, many hundreds more in Indochina and In and to private gardens like Dr. Fairchild's dia, where also Citrus culture is an ancient Kampong, and Col. Montgomery's Arboret art. Here is to be found the richest store um, it has been possible for nearly half of Citrus varieties in the world, at least a century to grow to full maturity in the ten times as many as we know in this continental United States all the many tropi country. cal relatives of Citrus that have so far been The large importations- of Citrus introduced. from Asiatic regions liable to carry Citrus During the campaign for eradication of canker, to say nothing of diseases and in , an appropriation was made sects as yet unknown in New World, nec to the Bureau of Plant Industry in 1915 essitated the creation by Mr. T. Ralph Rob to enable a search to be made for canker- inson, Eugene May and myself of a system resistant Citrus varieties. These funds per which we called aseptic plant propagation mitted me to undertake an exploration of (Dept. Agric. Circular 299 (1923)) 1/ to the southeastern Asiatic region, China, In prevent any risk of introducing diseases or dochina, Thailand, ths Philippines and Jap pests, and at the same time secure vigorous, an to find canker-resistant varieties and to healthy propagation of all the numerous establish a field station in the Philippines species and varieties introduced from the to test the resistance of all obtainable Cit home of oranges, , and pummelos rus varieties to Citrus canker. This work in S. E. Asia and the adjacent islands. continued nearly two decades and resulted 1/ All of the papers mentioned here and in the discovery, description, and illustration very many others on the introduction of a vast number of Citrus varieties and of Citrus fruit trees, and their use for also canker-resistant wild relatives of Cit rootstocks or for -hybridizing are cited rus. Many of these had never before been in full in the bibliography of the first seen by the orange growers of Europe or of volume of "*' now the New World. being printed at the University of Cali A talented young Chinese graduate of fornia Press, Berkeley, California. 158 FLORIDA STATE HORTICULTURAL SOCIETY

Because of the long continued effort to we now know that there is every reason carry out the project approved at Pensacola to expect very great progress to be made half-a-century ago, we now have growing in improving rootstocks by hybridizing^ Cit in Florida more species and varieties of rus with' other related genera such as Pon- Citrus and related plants of the orange cirus, Fortunella, Microcitrus, Eremocitrus subfamily than are found in cultivation in and probably others not yet available for any Old World country! r trial. As soon as possible after the great freeze As soon as it became evident that Citrus of 1894 and '95, I made a number of hy could be hybridized with some of the related brids and originated the first and genera, even with some that looked very , which, when they fruited, were unlike Citrus, I began to study the botany described and figured by Dr. Herbert J. of the Orange subfamily. Webber. Impressed by the favorable recep In my first effort to study the Australian tion given to these new Citrus fruits, I be desert , a gray-green shrub or small gan in 1909 hybridization work on a much tree, able to live in very dry situations in larger scale, using the to hybridize the interior of Australia, I found only a with the lime arid with the yery hardy eit- single herbarium specimen of it in the Unit ranges. Thanks to the active cooperation of ed States and this specimen had only a the experts associated with me, Mr. T. Ralph single flower. I examined it carefully and Robinson, E. M. Savage, and Eugene May, found it very like a Citrus flower only very Jr., many hundreds of hybrids were made much smaller. Up to this time no taxonomic using more and more hardy, saline-resistant botanist had suspected that it could be a or boron tolerant Citrus relatives, such as Citrus highly modified to grow in semiarid the Australian species of Microcitrus and regions. It had been referred to the genera the anomalous desert-inhabiting, gray-green and . Strong efforts were Eremocitrus glauca. now made to secure seeds of this plant, This large-scale, long-continued hybridiza and in February, 1911, dried fruits con tion work carried on actively for more than taining viable seeds were introduced by Dr. 40 years—1893 to 1934—under my general David Fairchild from Queensland, Australia, direction showed the unexpectedly high value and distributed under Plant Introduction of many wild relatives of Citrus for use as number 29660; and before the end of March, rootstocks, better adapted to certain soil the tiny seedlings had been approach- or climate conditions than any species or grafted successfully on Citrus. I created variety of Citrus yet tested. a new genus, Eremocitrus, for this plant, Dr. H. J. Webber, for many years Direc in May 1914, and a few years later, trees tor of the Citrus Experiment Station of the growing at the U S. Experiment Date Gar University of California, at Riverside, Cali den at Indio began to fruit. When the seeds fornia, began some 18 years ago a large- germinated, it was found that a consider scale, rootstock experiment. I went over able portion of them (roughly 20-25 per these experiments with him in March and cent) were hybrids due to the pollination April of this year (1943) and am permitted by the desert flowers from near-by to say that of all the many rootstocks tested Citrus trees by bees. v for hardy valencias, and other Citrus These hybrids grew much more rapidly fruits, the two which made the best show than the unhybridized Eremocitrus seedlings ing for 17 years were the Sampson and were found to make good rootstocks and the Morton , both of which I for oranges and lemons and to be able to made in 1897 at Eustis, Florida. grow in soils too saline or with too heavy In view of the very many hardy, vigorous, a boron content to support orange or lemon salinity-resistant and boron-tolerant hybrids trees grafted on any species of Citrus root. FLORIDA STATE HORTICULTURAL SOCIETY 159

The fat was now in the fire and I felt it cies comprised in the group of True Citrus necessary to start serious taxonomic studies Fruit Trees can be hybridized and, as a on all the plants belonging to the Orange matter of fact, hybrids have already been subfamily, studies which have occupied me made with all but one genus, , re for more than 30 years during which time cently discovered in New Zealand north of I have published some 25 taxonomic papers the Solomon Islands. As soon as the war is with numerous illustrations and two general over it will be easy to secure seeds of Cly accounts of Citrus and related plants. The menia by air express and grow it in Coco first of these general accounts was in Dr. nut Grove where it can be tested as a root- L. H. Bailey's Standard Cyclopedia of Hor stock and for hybridizing. The hybrids made ticulture, Vols. 1-6, 1914-1917, consisting in this country, most of them in Florida of 37 short articles discussing only the more since 1927, have included numerous tangelos important species almost all of them grow as well as of very high quality but ing in the United States. Just a few weeks not more resistant to cold than the parent ago, after more than 9 years' work, I fin species, Citrus sinesis (orange), C. reticu- ished correcting the proof of the "Botany lata, (), C. paradisi (). of Citrus and its Wild Relatives of the Or The hybrids of the West Indian ange Family" in 345 pages with 50 illus lime and one of the kumquats are very like trations. This is a manual of all the spe limes in quality and much more cold resist cies known of all the genera belonging to ant. The Lakeland limequat has grown and the Orange subfamily. This work will appear fruited very well both in Florida and in as Chapter IV of Volume I of "The Citrus California. A complex hybrid like the Thom- Industry", under the Editorship of Dr. Her asville , made by crossing a bert J. Webber and Dr. L. D. Batchelor, hardy citrange with a semi-hardy kumquat, and will be published in 1943 by the Uni is a promising subacid fruit for home gar versity of California Press. dens in warmer parts of the cotton belt in This is the first work since 1861 to dis the Southern States. cuss all the known genera and species of the The remarkable Altamaha (or Glenn) Cit- Orange subfamily and their relationships. rangedin, a small but beautiful, fine-flavored, It includes 203 species belonging to 33 gen acid fruit, which first fruited in the Alta era, included in two great tribes which we maha River valley in central Georgia, . in might call the Wampee tribe () cludes the blood of four distinct species of and the Citrus tribe (). It is diff Citrus fruit trees, the sweet orange and icult to graft Citrus fruit trees on plants the (the parents of the of the Wampee tribe but it has been done citrange) and a kumquat and a sour man on two different genera of this tribe in the darin (the parents of the calamondin). Washington Citrus greenhouses. The Citrus Three different genera, Citrus, Poncirus, and tribe includes 28 of the 33 genera of the Fortunella are blended in this hybrid. Orange subfamily and 124 of the 203 spe Altogether, first and last from 1893 to cies. It is divided into 3 subtribes each con 1943, many tens of thousands of scrupu taining 3 groups of genera. The cultivated lously safeguarded cross pollinations of Cta Citrus fruits are all included in the subtribe rus species and wild relatives have been Citrinae with 13 genera. Citrus has been made under my supervision by my associ grafted successfully on 9 of these genera ates, H. J. Webber, T. R. Robinson, E. M. which have been introduced into this country. Savage, Eugene May, Jr., and by myself. Citrus has already been hybridized with Several thousand hybrids have been grown every one of them, and probably can be long enough to select the healthy vigorous grafted on the 4 genera not yet introduced. ones, of which many hundreds have fruited Doubtless all of the 6 genera and 28 spe and been carefully tested. No such array 160 FLORIDA STATE HORTICULTURAL SOCIETY

of known hybrids between so many Citrus budded on young vigorous tabog seedlings, fruits and wild relatives has ever before and provided the grafted trees are planted been made in any country. Fortunately Mr. in a Citrus house, where the soil is kept E. M. Savage is continuing this breeding warm (not hot) all winter. work under the direction of Dr. Frank It is very possible the Philippine Tabog Gardner at Orlando, Florida, in charge of may prove to be a good rootstock for Cit the Bureau of Plant Industry Horticultural rus in tropical countries where the soil is Station (1). warm all winter long. There is a great future for such' hardy Citrus has been grafted even on plants hybrids and others now being tested for belonging, to the tribe Clauseneae, plants culture in home gardens north; of the zone very different from Citrus in flower and where oranges, grapefruit, lemons and limes leaf characters. A grapefruit tree was grown are now grown. (See page 161). for many years in the B. P. I. Citrus green The present showing as to the species of house at Washington, grafted on the Wam- Citrus and of related genera of the Orange !pee, Clausena Lansium, but such grafts subfamily now growing in this country is lived only when was used as as follows: an interstock and only if a few short sprays It is probable that most all of the species of wampee foliage were allowed to develop of the tribe Citreae are closely enough re at the top of the Wampee rootstock, just lated to pur Citrus fruit trees to be used below the graft union. The grapefruit tree as rootstocks although in many cases inter ripened fruit for many years, but remained mediate stocks may be necessary for good dwarf with a bad union where the rough growth and long life of the Citrus scion. lemon graft joined the Wampee rootstock. It has been proved repeatedly As there are 22 other species in the gen through numerous tests made by my staff of us Clausena besides the Wampee, it is prob workers in the Bureau of Plant Industry able that many of these could support Cit that Citrus can be grafted successfully on rus scions if proper interstocks were found. all of the other members of the subtribe If we assume that Citrus can be grafted Citrinae available for trial. , Hes- on 9/10 of all of the 124 members of the perethusa, Atalantia and have some Tribe Citreae, and on one-quarter of the species on which Citrus grafts well. 79 members of the tribe Clauseneae, we Citrus can be grafted also on some of would get the amazing total of 130 species the members of the subtribe Triphasiinae, of possible wild-relative rootstocks for our but so far, such grafts have made only slow Citrus fruit trees! growth. By cross-pollinating these wild relatives Citrus can be grafted on at least 2 gen of Citrus, it is certain that many hybrids of era of the Hard-Shelled Citroid Fruit Trees, great vigor could be secured, some of which' belonging to the subtribe Balsamocitrinae. would make superior disease-resistant root- Citrus grows very well on the Philippine stocks for Citrus. Tabog, glutinosa, provided it is The hybridization of Citrus Fruit Trees (1) Many papers on Citrus hybrids are cit and their wild relatives is by no means as ed in the bibliography of my chapter easily done as the grafting of them. Hy "The Botany of Citrus, etc.", under brids have been made between some of the the names of H. J. Webber, H. B. species of all the True Citrus Fruit Trees— Frost, T, Ralph Robinson, and myself. Fortunella, Eremocitrus, Poncirus, Microcit- In many cases these papers have co rus and Citrus (Clymenia is not yet avail authors. A good resume of Citrus breed able but probably could be hybridized with ing work is given in the Yearbook of all of the genera just listed). These genera the Department of Agriculture for 1937. contain 29 species and ah enormous num- FLORIDA STATE HORTICULTURAL SOCIETY tet ber of hybrids can be made between them. pect the origination of more and more use Complex hybrids, such as Citrangequats, ful complex Citrus hybrids adapted to grow in regions too cold for pure Citrus varieties, Citrangeremos, Citrangedins and Faustri- and also other valuable hybrids able to medins, which contain blood of three gen withstand salinity or slight excess of boron era, are some of them of decided vaiue in the soil. We now have enough material and more of them should be made as soon to work efficiently on such hybridizing—we as possible. There is every reason to ex did not have in 1893!

Census of the tribes, subtribes, genera and species of the Orange subfamily in the world and the number growing in the United States.

The Orange Subfamily 33 genera, 24(75.7%) in U.S.A. 203 species, 44(21.7%) in U. S. A

1. The Wampee Tribe (Clauseneae) 5 genera, 4(80%) in tL S. A. Very Remote and Remote Citroid Fruit Trees 79 species, 6(4.8%) in U. S. A.

Subtribe I. Micromelinae. Very Remote Citroid Fruit Trees

Micromelum 9 species, none in U. S. A. -

Subtribe II. Clauseninae. Remote Citroid Fruit Trees

Glycosmis 35 species, 1(2.3%) in U. S. A^ Clausena 23 species, 1(4.3%) in U. S. A. (G)* Murraya 11 species, 2(18.2%) in U.S.A. (G)

Subtribe III. Merrilliinae. Large-fruited Remote Citroid Fruit Trees

Merrillia 1 species, 1(100%) in U.S.A.

2. The Citrus Tribe (Citreae). 28 genera, 20(71.4%) in U. S. A. Citrus and Citroid Fruit Trees. 124 species, 39(31.6%) in U.S.A.

Subtribe I. Triphasiinae. 8 genera, 4(50%) in U.S.A. Minor Citroid Fruit Trees 46 species, 4(8.7%) in U.S.A.

Wenzelia 9 species, none in U. S. A. Monantho citrus 1 species, none in U. S. A. 4 species, none in U. S. A. Merope 1 species, none in U. S. A. Triphasia 3 species, 1(33.3%) in U. S. A. 1 species, 1(100%) in U. S. A. 12 species, 1(8.3%) in U.S.A. 15 species, 1(6.6%) in U.S.A.

Subtribe II. Citrinae. 13 genera, 9(70%) in U.S.A. Citrus Fruit Trees 65 species, 29(45%) in U.S.A.

5 genera, 2(40%) in U. S. A. Group A. Primitive Citrus Fruit Trees 14 species, 3(21.4%) in U.S.A.

Severinia 6 species, 2(33.3%) in U.S.A. (G) 5 species, none in U. S. A. 1 species, not in U. S. A. Limnocitrus 1 species, not in U. S. A. 1 species, 1(100%) in U/S.A. (G) 162 FLORIDA STATE HORTICULTURAL SOCIETY

„ ^T „._„_. m 2 genera, 2(100%) in U.S.A. Group B. Near-Citrus Fruit Trees 22 specieS) 5(22.7%) in U. S. A.

Citropsis 11 species, 2(18.2%) in U.S.A. (G) (H?) Atalantia 11 species, 3(27.3%) in U.S.A. (G) • „ „■ „ . m 6 genera, 5(83.3%) in U.S.A. Group C. True Citrus Fru>t Trees 29 speciegj 20(69%) in n. s. A.

Fortunella 4 species, 3(75%) in U.S.A. (G, H) Eremocitrus 1 species, 1(100%) in U.S.A. (G, H) Poncirus 1 species, 1(100%) in U.S.A. (G, H) Clymenia 1 species, not in U. S. A. Microcitrus 6 species, 4(66.7%) in U. S. A.. (G, H) Citrus 16 species 11(68.7%) in U. S. A. (G, H)

(Subgenus Eucitrus 10 species, 8(80%) in U.S.A.) (Subgenus 6 species, 3(50%) in U.S.A.)

Subtribe III Bahamocitrinae Hard-shelled^ , , „ ^ Citroid■. ., Fruit„ ,A Treesm ;i3gspecie's,(7 genera, all9(70%) in U.S.A.) in u. S.A.

Swinglea 1 species, 1(100%) in U.S.A. (G) Aegle 1 species, 1(100%) in U.S.A. 4 species, 2(50%) in U.S.A. . 2 species, 1(50%) in U.S.A. 1 species, 1(100%) in U.S.A. Feronia 1 species, 1(100%) in U.S.A. (G) Feroniella 3 species, 2(66.7%) in U.S.A. (G) * In this census tabulation the letter (G) following a genus means that a species of it has been grafted on a True Citrus Fruit Tree or vice versa; (H) indicates that a species has been hybridized with a True Citrus Fruit Tree.

Citrus relatives with edible fruit new to ful of marmalade all ready to eat as soon Florida as you cut, saw or break the shell open. It i j» r» l* •* *s said by experts to have valuable medicin- lnctian JSaelrruit ~ r ,,«,.,,, al qualities and a standard English book on The most important of these new rela- Indian horticulture states that very few tives of Citrus is the Baelfruit (Aegle Mar- English residents ever eat baelfruit unless raelos) of India. It is the most highly es- ordered to by their physician, but that then teemed fruit of the Orange subfamily in In- almost all of them continue to eat baelfruit dia and has been cultivated for ages. It is the rest of their lives. so different from Citrus in foliage, fruit Doubtless valuable vitamins account for flavor, etc., that at first it is hard to real- its habit-forming quality just as the flavone ize that it is a member of the tribe Citreae. giucosine aurantamarin found in the white It has a large, broadly oval or subglobose peei of the Seville orange makes orange fruit, 4—6 inches in diameter, with a shell marmalade a "must" breakfast dish for the almost as hard as a coconut. Inside this British and more and more Americans, hard shell there is a yellowish brown sub- Until a few years ago the baelfruit re- stance filling the broad spaces between the fuse(j to fruit anywhere in continental 10—15 narrow cells full of hairy seeds in United States, but in recent years, appar- a mucilaginous fluid. The yellowish brown entiy because of the increasing use of zinc filling between the narrow segments is more saits for orchard trees, especially Citrus like orange marmalade than any fruit. fruit trees, the Baelfruit has begun to fruit The baelfruit may be likened to a jar- freely in southern Florida, and now there FLORIDA STATE HORTICULTURAL SOCIETY 163

are many trees at the Sub-Tropical Station relatives thrive to perfection. of the University of Florida at Homestead There is every reason to expect the bael and at Dr. Fairchild's Kampong which fruit fruit to thriv- in Florida and to become freely every year. a prized breakfast marmalade, picked in a As long as the baelfruit did not fruit, it pot right from the tree. The striking vari was merely a botanical curiosity. Now that ability in botanically important leaf and most of tKe trees in Dade County, Florida, twig characters of the baelfruit trees now are fruiting freely, it promises to become growing in Florida makes it probable that a striking and popular new subtropical fruit. there must have been originally (and per Dr. Fairchild and I, as well as a few others haps still are) several different species of who have tested the fruits, find they. vary Aegle growing wild in the foothill regions greatly in size and flavor. Apparently all of the Himalaya Mountains in northern In the trees now growing in this country are dia. Seeds of fruits gathered from these seedlings with small, or at best, medium- different wild species during past ages and sized fruits. In India the best grafted varie planted side by side in dooryard or village ties bear fruits 6 or 7 inches in diameter. gardens all over India led to the produc Large baelfruits are much easier to eat than tion of hybrids through cross-pollination small ones, as the edible portion of the fruit by insects and gave rise to the present ex is composed of the greatly swollen mem ceedingly variable baelfruit trees found branes which separate the locules of the there. It is probable that careful search fruit. The homologous membranes are as in the regions of northern India would result thin as paper in an orange or grapefruit, in finding distinct species which could be but up to an inch or more thick in a large used by plant breeders to produce new and baelfruit, which makes them easily scooped superior baelfruit varieties with completely out with a spoon. deciduous leaves and hence able to endure The baelfruit has no close relatives in severe winter cold. Even now some baelfruit Asia, but no fewer than seven species be trees are deciduous in India and are able, longing to three genera are found growing when leafless, to endure temperatures as in tropical Africa from sea level to 3000 low as 17.5° F. without injury. feet altitude. One of these trees, the Niger W&mpees, Chinese and Indian ian powder-flask fruit, Afraegle paniculata, One of the favorite fruits of the two grows vigorously and fruits freely in south southeastern provinces of China; is the Wam- Florida and Mr. Jordahn, the superintend pee, Clausena Lansium. It has large leaves ent of Col. R. H. Montgomery's Arboretum and does not look at all like an orange at Coconut Grove (where one of the finest tree; its huge clusters of flowers are borne collections of Citrus relatives in the world at the end of the branches and numerous has been built up) grafted the baelfruit fruits looking very like pale, or even white, on young seedlings of Afraegle paniculata loquats, are produced. These fruits are in 1941. Late in May, 1943, Dr. Fairchild juicy and high-flavored, but vary greatly and I inspected them and were surprised in size and acidity. Up to now, only seed to find veritable young baelfruit trees with ling Wampees have fruited in Florida and a branched top 5—7 feet high, with abund all of them are, I believe, very acid. A re ant flowers on the upper branches. There cently published monograph describing 7 is another African species of Afraegle, A. cultivated varieties of the Wampee grown gabonensis, which also grows vigorously and in the vicinity of Foochow, China, lists 3 fruits freely in Coconut Grove, and Dr. sour varieties, 3 sweet subacid and one high Fairchild has already approach-grafted the ly flavored sweet varieties. Some of these baelfruit successfully on it in his Kampong, varieties are as much as' 1%-inches long where so many Citrus varieties and Citrus and % of an inch wide, 164 FLORIDA STATE HORTICULTURAL SOCIETY

The harvesting of Wampee is very easy contain the blood of trifoliate orange as because of the fact that they are borne in well as that of the sweet orange. clusters at the end of the branches. I have To summarize the. results of a search for seen one tree in Florida where the fruits the cultivated Citrus fruits and their wild were densely crowded and were almost relatives of the Old World, it appears that seedless, a few dried on the tree. Years many of the cultivated Citrus fruit trees ago we were able to graft Wampee on Cit are accidental hybrids which1 have arisen rus stock which dwarfed the tree and would in Chinese or other Oriental village gardens lend itself to the Chinese system of grow during the three or four thousand year per ing Wampees on potted plants which could iod in which Citrus fruits have grown there. be placed on the table in front of the cus We now have available for use in the tomer, so he could pick them straight from New World also many species of Citrus and the potted plant. of closely related genera not found in China The Wampee is especially interesting for but native to the East Indian Islands, New further trial in Florida. Another species Guinea and Australasia. By using them we called Indian Wampee, Clausena dentata have already bred new Citrus fruits of high var. dulcis, known to the natives of Anai- value, and new rootstocks as well. malia Hills in Madras Presidency as "Mor Citrus fruit trees can be grafted on a Koorangee", has globose fruits the size of great number of wild relatives, some of a large cherry with very delicious flavor. them so remote botanically from Citrus as The tree attains a height of 30 feet and is to be difficult if not impossible to hybridize. several feet in girth. It grows at an alti Several such remote wild relatives have al tude of 1000 to 4000 feet, flowers in April ready been tested for many years and have and produces fruits in May and June. This made excellent rootstocks for Citrus.. Other will, without doubt,.be introduced from In new rootstocks obtained by hybridizing Cit dia as soon as war conditions permit, and rus with species of other genera not too hybrids will be made with the Chinese Wam distantly related have already proved to be pee as soon as the Indian Wampee is old of high value to our Citrus growers. enough to flower. There are several new fruit trees not Another edible species of this same genus, closely related to Citrus that are promising Dr. Henry's Wampee, the small-fruited hardy for culture in this country, such as the bael- Clausena dentata var. Henryi, native around fruit with a tasty marmalade-like pulp en Ichang in central China and said to be cul closed in a hard shell. The Chinese and In tivated in Hupeh Province, would probably dian Wampee and their hybrids may become hybridize with the Indian Wampee as both valuable fruit trees in Florida and Puerto are varieties of the same species, Clausena Rico. dentata. Such a hybrid would probably cross Many of the newly introduced species of more easily with' the Chinese wampee than Citrus and its wild relatives, and hybrids would the unhybridized Indian Wampee, just which have been made with them in this as the kumquats (Fortunella sp.) are almost country, are plants of great ornamental impossible to hybridize with the trifoliate value destined to have a place in subtropi orange (Poncirus) but cross freely with the cal gardens for avenues, hedges or border citrange, which as can be seen at a glance, plants.

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