500 



BOTANY OF THE LIVING PLANT 



vegetative propagation by " gemmae." But this gametophytic 

 budding is less common here than in the Bryophytes. 



The dependence on moisture is still more obvious in the behaviour 

 of the sexual organs which the prothallus bears. These are male and 

 female, and they may be found on the same prothallus (Fig. 392), or 

 on different prothalli (Fig. 393, 1). In the former case the antheridia, 



Mature prothallus of Dryopteris Filix-mas, as seen from below, bearing antheridia 

 among its rhizoids, and archegonia near to the apical indentation. (After Kny.) 



or male organs, commonly appear first, and the archegonia, or female 

 organs, later. There may thus be a separation of the sexes either in 

 time or in space. The flattened prothallus of the ordinary cordate 

 type usually bears both sex-organs. When growing under normal 

 circumstances on a horizontal substratum it produces them on its 

 lower surface, the antheridia in the basal or lateral regions, the 

 archegonia upon the massive cushion. The latter develop in acropetal 

 order, the youngest being nearest to the incurved apex of the pro- 

 thallus. The position of the sexual organs is evidently favourable 



