130 GROWTH OF PLANTS 



Let us examine the application of the Flemion method to several different donnant seeds 

 shown in Figure 50. In A are embryos of Rkodotypos kerrioides. Beginning at the left is an 

 embryo just removed from a swollen seed of 1937 crop; the next 5 in succession are sample 

 embryos from the seed crops of 1932, 1934, 1935, 1936, and 1937, all removed and kept in the 

 germinator five days in 1937. Note that the embryo of the 1932 crop is disintegrating and 

 note the increased growth from the 1934 crop to the 1937. In excised "dormant" Rkodo- 

 typos embryos both the cotyledons and the roots grow rather promptly, though not nearly as 

 promptly as the low-temperature after-ripened embryos, as we have already seen; and the 

 rate of growth increases with vigor of the embryos and decreases with the age of the seed. 

 The behavior of embryos from the 1932 and 1934 embryos kept on moist filter paper 5 addi- 

 tional days, or 10 days in all, are shown in B. The 1932 embryo is dead and decaying, while 

 the 1934 embryo has such low vigor that it has not enlarged, although it has developed more 

 clilorophyll. It is evident that this test shows not only the embryos that are alive but also 

 the relative vigor of the living embryos of the several crops. 



Apple embryos are shovvm in C: the one at the left, a freshly excised embryo, followed by 

 2 dead embryos and 2 hve ones after 6 days on moist filter paper. The apple embryo is more 

 sluggish in its early growth than the Rkodotypos embryo. There is merely an enlargement and 

 the greening of the cotyledon in contact with moist filter paper in some embryos; in others 

 both the cotyledons and the roots grow in the 6-day test. 



In D Crataegus Cnis-gaUi embryos are shown in a 10-day test run started February 1, 1938. 

 Begiiming at the left, first, second, and third are embryos from 1928, 1930, and 1933 crops 

 respectively, all non-viable. The fourth embryo is of the 1935 crop which has not yet had 

 time to enlarge. The fifth embryo is of the 1936 crop in which the intact carpel had been 

 stratified one year at 5° C (41° F) ; but the embryo had not after-ripened under this condition, 

 due to the resistant coat, as shown by the growth of only the cotyledon in contact with the 

 moist filter paper. Crataegus embryos are very sluggish in their early growth, and manifest 

 their viability in these tests by the enlargement and greening of the cotyledon in contact with 

 the moist filter paper and their lack of viabiUty by decay. The test period for these should 

 run for several weeks. 



Sorbus aucuparia embryos are shown in E: beginning at the left is a freshly excised embryo 

 of Sorbus aucuparia; embryo of the 1930 crop, decaying; and embryo from the 1937 crop with 

 cotyledons enlarged and green. The second and third have been on moist filter paper for 6 days 

 beginning November 18, 1937. The dormant Sorbus embryos are more sluggish in their growth 

 than dormant Rkodotypos embryos and less sluggish than apple and Crataegus embryos. 



Witch-hazel embryos appear in F after 5 days on moist filter papers (November 18, 1937), 

 1934, 1935, and 1936 crops. The one-year-old embryos gave good growth, the two-year-old 

 embryos little growth, and the three-year-old none. In G is shown the reaction of the 1934 

 embryos (dead) and the 1936 embryos, high viability, to para-dinitrobenzene-ammonia 

 treatment; in H is the reaction of the same to 1 per cent potassium tellurite treatment; and J 

 shows the development of these embryos after 5 days on moist filter paper. The color diEfer- 

 ence from the reduction of the two chemical compounds is not very conclusive as to degree of 

 vitality. 



Prunus americana embryos are shown in K, all from viable seeds after several weeks on 

 moist filter paper. These embryos are extremely sluggish in their early growth and show 

 viability mainly by slow growth and greening of the cotyledon in contact with the moist filter 

 paper and by the occasional growth of a root. The dead embryos soon disintegrate. 



The fringe-tree embryos appear in L. In order, beginning at the left, are: dead embryo and 

 live embryos after 4, 6, and 20 days. In M are Douglas fir embryos: beginning at left, freshly 

 excised, viable, and non-viable embryos after 4 days. Pinus rigida embryos are shown in N. 

 From left to right, freshly excised, dead embryo, embryo with low vitality, and one with high 

 vitality after 8 days on moist filter paper. In selecting the embryos for this plate (Fig. 50), the 

 embryo that most nearly represented the average growth or behavior in duplicate cultures of 

 at least 50 embryos was used. 



