THALLOPHYTA— ALG^ 



65 



Fig. 816. 



from near its base. These cells are separated from it by cell 



walls, but the oosphere itself remains 



naked. 



The oogonium does not open, but 

 the antherozoid makes its way 

 through the cell-wall, which under- 

 goes a sort of mucilaginous degene- 

 ration. The fertilised oosphere after 

 fusion with it becomes an oospore 

 with a very thick wall. 



The germination of the oospore 

 is peculiar ; a transverse wall is 

 formed near the apex and a small 

 cell is so separated from the rest. 

 The latter part of the oospore takes 

 no part in the further development, 

 but remains as a store of nutriment 

 for the young embryo. The small 

 cell divides into two, and fi-om one 

 of these the new shoot is developed, 

 the primary root arising from the 

 other. A small pro-embryo is thus 

 produced which bears a single whorl 

 of leaves and a few adventitious 

 roots. The Chara plant arises as a 

 bud upon this, its apical ceU being 

 differentiated among the whorl of 

 leaves ijlg. 816, g). 



In the genus Nitella the stem is 

 much more slender than in Chara, 

 and it is not furnished with a cortex. 



There are no asexual cells pro- 

 duced, but vegetative propagation is 

 sometimes brought about. Certain 

 branches of peculiar form may be- 

 come detached from the parent and 

 grow into new plants; or gemmse 

 may be developed upon the under- 

 ground nodes. 



Not producing any asexual cells, 

 Chara does not exhibit any alternation of generations, 

 plant is the gametophyte. 



Fig. 816. Pro-embryo of Chara 

 fragilis. .-.p, Genoiuatiug spore. 

 i, (/, q, pi. The pro-embryo. 

 At d are the rliizoids, u: w'. 

 Primary root. g. First leaves of 

 the second generation, or Chant 

 proper. After Pringslieim. 



The 



VOL. II. 



