312 



PART IV. CLASSIFICATION. 



become mucilaginous and disorganised, so that the oosphere is 

 placed in communication with the exterior by the canal of the 

 neck. Fertilisation takes place when the plants are more or less 

 covered with water from rain or dew. Then the antheridia dehisce, 

 the spermatozoids are set free, and, since the male and female 

 organs are at no great distance, they, swimming by means of their 

 cilia, come into the neighbourhood of the archegonia ; they are 



attracted to enter 

 the necks of 

 archegonia by the 

 escaping mucilage 

 formed by the 

 disorganisation of 

 the canal - cells, 

 which contains 

 cane-sugar which 

 substance has been 

 shown to be 

 especially attrac- 

 tive to them (see 

 p. 220). One of 

 the entering sper- 

 matozoids travels 

 down the canal 

 to the oosphere, 

 which it pene- 

 trates, the nu- 

 cleus of the sper- 

 matozoid fusing 

 with that of the 

 oosphere. Fer- 

 tilisation is now 

 complete ; the 

 fertilised oosphere 

 surrounds itself with a cell- wall and becomes the oospore, which 

 begins to divide and to develope into the sporophyte. 



The effect of fertilisation is not confined to the oosphere. The 

 adjacent tissue of the shoot is stimulated to growth, and in some 

 forms (Sphagnaceae) it grows out into a long leafless stalk, the 

 pseudopodium, which carries up the fertilised archegonium on its 

 apex. The venter of the archegonium also grows, forming, either 



FIG. 194. Marchantia ^olymorpha. A young ; -B mature, but 

 unfertilised, archegonium. C Fertilised archegonium, with 

 dividing ooepore. fc' Neck-canal-cells ; fc" ventral canal-cell ; 

 o oosphere ; pr perigynium. (x 640 : after Strasburger.) 



