shoot tip of Abies conco/m·. Amer. J. Bot. 41:749-759. 46:110-118. STERLING, C. 1946. Organization of the shoot PoPHAM, R. A. 1960. Variability among vegeta­ of Pseudotsuga taxifo/ia (Lamb.) Britt. I. tive shoot apices. Bull Torrey Bot. Club Structure of the shoot apex. Amer. J. Bot. 87:139-150. 33:742-750. RoMBERGER, J. A. 1963. Meristems, growth, TEPPER, H. B. 1963. Dimensional and zonationa! and development in woody plants. U. S. variation in dormant shoot apices of Pinus Dept. Agric., Forest Service Tech. Bull. 1293. ponderosa. Amer. J. Bot. 50:589-596. 214 pp. VANDEN BoRN, W. H. 1963. Histochemical SACHER, J. A. 1954. Structure and seasonal studies of enzyme distribution in shoot tips activity of the shoot apices of Pinus /amber­ of white spruce (Picea g/auca (Moench) Voss). tiana and Pinus ponderosa. Amer. J. Bot. Canad. J. Bot. 41:1509-1527.

Inheritance of Cotyledon Number in Douglas-Fir

Note by Frank Sorensen

Abstract. Intraspecific crosses were made using five different pollen mixes on the same Pseudostuga menziesii seed tree. At germination, it was found that average cotyledon numbers of the progenies could be used to verify several hybrid parentages even though average numbers differed by one cotyledon or less.

Cotyledon number has recently been used to could be determined without damage to the verify a hybrid between noble fir (Abies procera seedlings as soon as seedcoats are shed, or even Rehd.) and California red fir (Abies magnifica earlier if the seed can be sacrificed. In this report, A. Murr.).1 For these species, cotyledon numbers a small test, involving several crosses using a were different, ranging from 4 to 7 in noble fir common female parent, is described. Some pro­ and from 7 to 11 in California red fir. Douglas­ genies did show significant differences in average fir (Pseudotsuga menzzestt (Mirb.) Franco) cotyledon number, thus verifying their diverse cotyledon numbers range at least from three2 hybrid parentages. to 113. Can this wide variability in cotyledon number be used to confirm intraspecific crosses in Douglas-fir? If so, genuine crosses could be Materials and Methods recognized early because cotyledon numbers Female strobiles of a single tree at 4,400 feet m the central Oregon Cascade Range were pol­ linated by the following: 1 Silen, Roy R., Critchfield, William B., and 1. A mixture from five trees growing at 4,000­ Franklin, Jerry F. Early verification of a hybrid foot elevation about 1 mile east of the female between noble and California red firs. For. Sci. parent; 11: 460-462.

2 Personal observation. The au thor is Research Forester, Pacific Northwest Forest and Range Expt. Sta., Forest 'Greathouse, Thomas. Personal communica­ Service, U.S. Dept. of Agric. portland, Oregon tion. Manuscript received July 14, 1965.

volv,mc 12, number 2, 1966 I 175 TABLE 1. Average and range in cotyledon 5. Wind-pollinated seeds were also collected number in seedlings from five intraspecific from the female parent. crosses of Douglas-fir, by elevation of Twenty-four germinated seeds from each cross parents. were planted, three per plastic pot following a randomized block design in forest soil from the central Oregon Coast Ranges. Pots were placed Elevation of parents' Cotyledons in a growth c.hamber under a 16-hour photo­ period (light intensity about 1,100 foot-candles) (feet) Average Range of and a 16-hour thermoperiod (22°C day tempera­ number number ture, 10°C night temperature). Average seed weights of the five lots were very nearly the same. 4,400 wind pollinated 6.62 5-8 Number of cotyledons was counted 30 days after 4,400 X 4,00()2 7.00 6-8 planting. Cotyledon length, when measured, did 4,400 X 2,00()2 7.65 6-9 not differ among crosses. 4,400 X 7002 7.39 6-9 Basic unit of observation for analysis of vari­ 4,400 X 2002 6.88 6--8 ance was average number of cotyledons per seedling on three seedlings of one cross in a single pot, except in one pot in which one germ­ LSD.05 based on ~he Duncan test is 0.44 cotyledon; LSD.o, is 0~58 cotyledon. minating seedling failed to develop cotyledons. 'Female parent, identified by altitude, is listed first; male parents, similarly identified, Results and Conclusions are listed afterward. Average cotyledon numbers for seedlings of the 2Pollen parentage is a composite or mix of five families are given in Table 1. An analysis four to seven individuals, as described in the of variance was performed with 4, 7, and 28 text. degrees of freedom for crosses, replicates, and error, respectively. The F-value was 9.02, significant at the 1-percent level. These results indicate rather strong control 2. A mixture from four trees growing at 2,000­ of cotyledon number. In fact, genetic variance, foot elevation about 30 miles west of the female when expressed as a proportion of genetic plus parent; remainder variances, is equal to 0.53. 3. A mixture from seven trees growing at Thus, comparisons reveal that hybridi ty in 700-foot elevation about 40 miles west of the Douglas-fir can be confirmed at germination time female parent; by average cotyledon number, even when: (1) 4. A mixture from four trees growing at 200­ numbers on individual seedlings range from 5 to foot elevation about 50 miles west of the female 9; and (2) average cotyledon numbers of crosses parent. vary from 6.6 to 7.6.

17G I Pore.~t Scitnc~