THALLOPHYTA— ALG.E 



65 



from near its base. These cells are 

 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 from one 

 of these the new shoot is developed, 

 the primary root arising from the 

 other. A small pro-emhryo is tlius 

 produced which bears a single whorl 

 of leaves and a few adventitious 

 roots. The Chara plant arises as a 

 bud upon this, its apical cell being 

 differentiated among the whorl of 

 leaves {fig. 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 gemmae 

 may be developed upon the under- 

 ground nodes. 



Not producing any asexual cells, 

 Chara does not exhibit any alternation 

 plant is the gametophyte. 



separated from it by cell- 



FiG. 81(3. 



Fig. 816. Pro-embryo of Chara 

 fragilis. sp. Germiiiatiug spore. 

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

 At (I are tlie rliizoids, w. le'. 

 Primary root. g. First leaves of 

 the second generation, or Chara 

 jiroper. After Pringsheim, 



of generations. The 



VOL. II. 



