FROM THE USUAL STRUCTURE OF SEEDS. 305 



certain relation to the central cavity where the embryo is 

 afterwards formed, and which, filled with a glairy ilnid, is 

 distinctly visible before the separation of the seed. It is a 

 curious consequence of this tardy evolution of the embryo, 

 which in some cases does not become visible unless the [no 

 seed be placed in a situation favorable to germination, that 

 very different directions may be given to its radicular extre- 

 mity, according to circumstances which we have it in our 

 power to regulate. 



There is a fourth kind of anomaly in the structure of 

 certain seeds, which, as I have formerly described it,^ 1 

 shall here notice in a few words. It is that wdiich takes 

 place in certain Aroidcce, especially in some species of 

 Caladiiim. In these, the nucleus of the seed is not pro- 

 perly a monocotyledonous embryo, but has an appearance 

 {uul economy more nearly resembling those of the tuber of 

 a root ; for, instead of being distinguishable into a cotyledon, 

 a plumula and radicula, and of germinating in a determi- 

 nate manner and from a single point, it is composed of a 

 mass wdiose internal structure is uniform, and on the sur- 

 face of which frequently more than one germinating point 

 is observable. 



None of these anomalies appear to me materially to 

 lessen the importance of the characters derived from the 

 seeds of plants ; but they evidently render a minute atten- 

 tion to every circumstance absolutely necessary in all 

 attempts either to deduce affinities or establish genera from 

 this source ; and they especially demonstrate the neces- 

 sity of carefully ascertaining the state of the unimpreg- 

 natcd ovarium; for, wdiile its structure remains unknown, 

 that of the ripe fruit can never be thoroughly understood. 



1 Prodr. Flor. Nov. Holl. p. 335. 



