REPROPUCTION. 615 



tium with the trichogyne the carpogenous cell or cells are at 

 once fertilised and stimulated to cell-formation, and accordingly 

 they produce the carpospores, each of which is physiologically 

 equivalent to a zygospore or an oospore, inasmuch as it is, 

 like them, a sexually produced spore. 



The peculiarities of the sexual process in some of the Floridese are so 

 striking as to merit brief mention. 



In the Corallineae, according to Solms-Laubach, the procarpia are 

 produced several together in a conceptacle ; it is, however, only the 

 central procarpia of the group which are capable of being fertilised, and 

 it is only the peripheral procarpia which produce carpospores ; the 

 former, in fact, are functionally only trichogynes, the latter only carpo- 

 gonia. After the fertilisation of the central procarpia, the carpogonia of 

 the whole of the procarpia fuse together to form one large cell from the 

 periphery of which the carpospores are budded off; thus a number of 

 procarpia eventually give rise to only one cystocarp. 



This tendency to a physiological division of labour is more marked in 

 Dudresnaya and a few other Florideae. In these, some of the procarpia 

 are altogether destitute of a trichogyne, whereas others possess one. 

 The spermatia fertilise those procarpia which possess a trichogyne, but 

 these procarpia do not produce carpospores. There grow out of them 

 filaments which grow out towards the procarpia which have no trichogyne 

 and fertilise them, and these then produce carpospores. 



In the Phanerogams the sexual organs are essentially of 

 the nature of the archegonia and antheridia mentioned above. 

 In most of the Gymnosperms the female organ, though com- 

 monly termed a corpusculum^ is in fact nothing more or less 

 than an archegonium. In the Angiosperms the female organ 

 is represented by a group of three cells, termed the egg- 

 apparatus, one of the three cells being the oosphere and the 

 other two the synergidcs. There is some ground for the view 

 that these three cells represent three much reduced archegonia, 

 only one of which is directly concerned in the sexual process. 

 The male organ of the Phanerogams is a unicellular filament 

 known as the pollen- tube. It is a male organ, the protoplasmic 

 contents of which undergo imperfect differentiation into male 

 gametes. Just before fertilisation takes place the pollen-tube 

 being already in close relation with the female organ the 

 apex of the pollen-tube contains protoplasm and a nucleus, 

 which Strasburger has termed the generative nucleus. In most 



