50 



ON SEEDLINGS 



fore seek some other explanation, and I will suggest the 



following. 



In most of the species which I have examined, when the 



cotyledons remain in the seed they do not leave the ground. 

 In some cases, however, as in Anona 

 (fig. 96), the hypocotyl is long, stout, and 

 rises in the form of a loop during ger- 

 mination, while the cotyledons, which at 

 first are very small, gradually increase 

 almost to the length and breadth of the 

 seed, throw themselves into undulations, 

 and, it being perhaps on this account 

 impossible to withdraw themselves 

 from the seed, are eventually torn from 

 the hypocotyl. In Bignonia insignis, 

 again, the cotyledons, though flat and 

 leaf-like, are unable to emerge from, or 

 at any rate do not emerge from, the seed. 

 This may possibly give us a clue to such 

 cases as Eschscholtzia and Schizope- 

 talon, which, I would venture to suggest, 

 may have reference to the manner in 

 which the cotyledons free themselves 

 from the seed. If this is delayed, the 

 young plant suffers considerably, and 

 indeed often perishes . That the process 

 is not, however, so simple as might be 

 imagined, may be seen from the in- 

 teresting case afforded by the Cucurbi- 

 tacese, where, in Mr. Darwin's words, 1 

 'the seed-coats are ruptured by a 

 curious contrivance, described by M. 

 Flahaut. A keel or peg is developed 

 on one side of the summit of the 

 radicle or base of the hypocotyl ; and this holds down the 

 lower half of the seed-coats (the radicle being fixed into 



1 Movements of Plants, p. 102. Bower has pointed out in Welwitschia that 

 a corresponding process serves to absorb the endosperm, acting in fact as a 

 feeder to the young plant (Quart. Journ. Micr. Sci. vol. xxi.). 



FIG. 96. Germinating 

 seedling of Anona. 



