CHAP. VI. FUNCTION OP REPRODUCTION. 287 



ovules arranged on the placenta of a carpel an organ 

 which we have considered to be formed on this prin- 

 ciple (art. 100.). 



(294.) Proportion between Seeds and Suds. An 

 argument in favour of the common origin of the em- 

 bryo and bud is deduced from the observed fact,, that 

 many plants which produce the one in abundance are 

 proportionally defective in the other kind. But this 

 after all may depend upon the plant not being able to 

 provide a sufficiency of nutriment for both. 



(295.) Hybrids. If the pollen of one species is 

 employed to fertilise the ovules of another, the seeds 

 will often produce plants which are strictly intermediate 

 in all respects between the two parents. Such produc- 

 tions are termed hybrids, and are manifestly analogous 

 to mules among animals. The conditions necessary for 

 the production of a hybrid are not ascertained, beyond 

 the fact that those species only are capable of forming 

 them which are nearly allied to each other, and are 

 either of the same genus, or of genera which scarcely 

 differ. It has been suggested that the possibility of 

 producing hybrids was limited to species whose pollen, 

 or rather whose pollen granules, were nearly of the same 



