32 GERMINATION. 



bryo was somewhat enlarged, the traces of its organiza- 

 tion were more evident, and its radicle was distinctly 

 visible. At the end of the third day, the exterior mem- 

 braneshad become brown, the rostel had burst through 

 it, and the plumelet had begun to expand. At the end of 

 the fourth day, the young plant had considerably en- 

 larged, and the nerves of the seminal leaves which 

 were still enclosed by the coats of the seed, had be- 

 come very perceptible. At the end of the ninth day 

 the plant had wholly escaped from the seed, though 

 the plumelet was still enveloped in the seminal leaves, 

 yellowish in its appearance but generally assuming a 

 tinge of green. At length its extrication was effected 

 and the rostel converted into a root ; the rudiments of 

 a stem developed ; and on the twentieth day the plant 

 was complete. 



The other example will serve to illustrate the 

 growth of seeds with one cotyledon. Some Rye was 

 planted in good soil, and at the end of the second hour 

 its radicle was discernible. At the end of twenty four 

 hours the embryo had escaped from its integuments. 

 On the second day the fibres of the root had augmented 

 but the leaves had not appeared. On the fourth day 

 the first leaf began to appear above ground, at which 

 time its colour was red. On the fifth day it had grown 

 to the length of an inch, and its colour was now green, 

 and on the sixth day the second leaf had appeared.* 



These effects are produced by the united influence 

 of air, water and heat. 



Homberg, a distinguished philosopher of Europe, 

 planted a variety of seeds under the exhausted receiver 

 of an air pump ; they rarely germinated, and in this 



* Keith. 



