Chap. X. SEXUAL RELATIONS OF PLANTS. 417 



seed, and this might possibly be a disadvantage. | 

 Delpino remarks that dioecious plants cannot spread so 

 easily as monoecious and hermaphrodite species, for a 

 single individual which happened to reach some new 

 site could not propagate its kind ; but it may be 

 doubted whether this is a serious evil. Monoecious 

 anemophilous plants can hardly fail to be to a large 

 extent dioecious in function, owing to the lightness of 

 their pollen and to the wind blowing laterally, with 

 the great additional advantage of occasionally or often 

 producing some self-fertilised seeds. When they are 

 also dichogamous, they are necessarily dioecious in 

 function. Lastly, hermaphrodite plants can generally 

 produce at least some self-fertilised seeds, and they are 

 at the same time capable, through the various means 

 specified in this chapter, of cross-fertilisation. When 

 their structure absolutely prevents self-fertilisation, 

 they are in the same relative position to one another 

 as monoecious or dioecious plants, with what may bo 

 an advantage, namely, that every flower is capable 

 of yielding seeds. 



2 a 



