SEED. 97 



vegetables having a distinct bark and pith. But, as above re- 

 marked, it has been discovered, that there are vegetables with 

 the above characteristics, whose embryos are unlike the one 

 above described, some having numerous cotyledons, others but 

 one, and others none. These apparent variations have been 

 sufficient to induce some botanists to reject entirely this classi- 

 fication, but we believe on very insufficient grounds, since by 

 careful observation nearly all these apparent discrepancies may 

 be reduced to a common principle ; and even if they could not 

 be explained at all, the foundation of the system would be 

 broader and firmer than any other proposed by the objectors to 

 this. Could we expect that the many thousand different species 

 of vegetables varying almost infinitely in their various parts, 

 could be reduced to three actual, invariable types \ It would 

 be requiring of this system, what has never been attained in 

 any other. 



171. Orders, in which more than two cotyledons are found, 

 are the Coniferae, in which they vary in number from two to 

 more than twelve ; in Boragineae and Brassicaceae, and some 

 other orders, there are four. In all these cases the cotyledons 

 are opposite. In the Horse-chestnut, there is apparently but 

 one cotyledon. Prof. Lindley says, that, by dissection, there is 

 a slit which indicates the division between the two bases of a pair 

 of opposite confluent cotyledons. Some such modification doubt- 

 less is the cause of all the variations from the common type. 



There are other cases in which no cotyledons exist. The 

 Cuscuta is an example of this kind ; but if the cotyledons are 

 leaves, we should not expect to find cotyledons in this genus, 

 since it has no leaves. There are other cases in which it is said 

 no cotyledons are discernible, but by more accurate observation 

 the cotyledons are found to exist in a rudimentary state, the 

 radicle seeming to be developed at their expense. 



The monocotyledonous embryo is very different in its structure 

 from the preceding. It is a homogeneous, cylindrical body, 

 tapering at both ends, with no distinction of radicle, plumula, or 

 cotyledon. 



What variations in cotyledons ? — 171. In what family more than two coty- 

 ledons ? In what species one or more ? How is the monocotyledonous 

 embrvo ? 



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