304 'DIFFERENT FORMS OF FLOWERS [1862. 



of each flower being mature at different periods. If I am right, 

 it is very advisable not to use the term " dioecious," as this 

 at once brings notions of separation of sexes. 



... I was much perplexed by Oliver's remarks in the 

 1 Natural History Review ' on the Primula case, on the lower 

 plants having sexes more often of the separated than in the 

 higher plants, — so exactly the reverse of what takes place 

 in animals. Hooker in his review of the ' Orchids ' repeats 

 this remark. There seems to be much truth in what you 

 say,* and it did not occur to me, about no improbability of 

 specialisation in certain lines in lowly organised beings. I 

 could hardly doubt that the hermaphrodite state is the 

 aboriginal one. But how is it in the conjugation of Con- 

 fervas — is not one of the two individuals here in fact male, 

 and the other female? I have been much puzzled by this 

 contrast in sexual arrangements between plants and animals. 

 Can there be anything in the following consideration : By 

 roughest calculation about one-third of the British genera of 

 aquatic plants belong to the Linnean classes of Mono and 

 Dicecia ; whilst of terrestrial plants (the aquatic genera being 

 subtracted) only one-thirteenth of the genera belong to these 

 two classes. Is there any truth in this fact generally ? Can 

 aquatic plants, being confined to a small area or small com- 

 munity of individuals, require more free crossing, and there- 

 fore have separate sexes ? But to return to one point, does 

 not Alph. de Candolle say that aquatic plants taken as a 

 whole are lowly organised, compared with terrestrial ; and 

 may not Oliver's remark on the separation of the sexes in 

 lowly organised plants stand in some relation to their being 

 frequently aquatic ? Or is this all rubbish ? 



.... What a magnificent compliment you end your review 

 with ! You and Hooker seem determined to turn my head 



* " Forms which are low in the scale of rank founded on specialisa- 

 scale as respects morphological tion of structure and function." — 

 completeness may be high in the Dr. Gray, in ' Silliman's Journal.' 



