DORMANCY IN SEEDS 93 



perature, 5° C (41° F), than they did at 10° C (50° F), and that 15° C 

 (59° F) or higher temperatures were unfavorable for germination. 



Dwarfish plants from dormant embryos. While dormant embryos grow 

 very slowly and show unusual correlations in the growth of their several 

 organs, Flemion ^^' ^^ was able to get seedlings from most of them by use 

 of proper methods; she finally obtained plants by transferring the seedlings 

 to soil. If placed in aerated water at room temperature so that water is 

 in contact with the whole surface of the embryo, excised Sorhus embryos 

 slowly form a seedling with the hypocotyl-radical elongated and both 



Figure 31. Rhodotypos kerrioides seedlings. Leji: grown from non-after-ripened 

 embryos. Right: grown from after-ripened embryos. 



cotyledons enlarged. Excised peach, apple, and hawthorn embryos can be 

 germinated by placing them in moist peat at 25° C (77° F). This treat 

 ment vrAX not give seedlings -^Wth dormant Sorhus embryos. The seedlings 

 gro-UTi from dormant embrj'os at higher temperatures form dwarfish tops, 

 although the root systems grow vigorously. Fig. 31 shows, at left, seed- 

 lings of Rhodotypos gro\\Ti from dormant embryos and, at right, seedlings 

 grown from low-temperature after-ripened embryos. The dwarfed seed- 

 lings have very short internodes and thick, deep green leaves in contrast 

 to the long internodes and thin, lighter green leaves of the seedlings from 

 the after-ripened embryos. Fig. 32 shows, at left, a seedling grown from 

 a dormant peach embryo and, at right, a seedling from a low-temperature 

 after-ripened embryo. In the dwarfed peach seedlings the internodes are 

 very short, the leaves thicker, deeper green, and shorter, and often much 

 deformed. To date, Flemion has been able to produce dwarfish seedlings 

 from all species and varieties of rosaceous seeds with dormant embryos 

 that she has tested, as well as A\4th witch-hazel seeds; but her studies have 

 not been extended to seeds of other families of plants \^'ith dormant 

 embryos. 



