STRUOTUUE AND DEVELOPMENT. 45 



and occurs on underground branches. These are clearly 

 metamorphosed whorls of branchlets, the cells corre- 

 sponding in number and position with those of normal 

 whorls (Fig. 15). From Dr. Giesenhagen's investiga- 

 tion it appears that the young plants arise from cells 

 at the base of the rudimentary branchlets on the 

 upper side, in the same position as normal branches in 

 the axils of normal whorls. 



In addition to the species mentioned, the occurrence 

 of bulbils is recorded in Nitella capiUarls, opaca, 

 translucens, gracilis and tenuissima and Chara scoparia, 

 vulgaris, rudis, hispida, horrida, intermedia and acu- 

 leolata. 



The oogonia and antheridia are produced 

 Eeproductive ^^ ^-^^ ^^^^ ^^^^^ ^^ ^^^^ branchlets, and 

 organs. , . 



occasionally also at the nodes at their 



base. In the several genera the origin and relative 

 position are somewhat different. The latter can of 

 course only be satisfactorily observed in monoecious 

 species and at the nodes where both organs are pro- 

 duced, and it is to these that the following particulars 

 apply. 



In Nitella the antheridia are solitary and are pro- 

 duced on a terminal outgrowth at the apex of a 

 branchlet-ray. The oogonia, which are solitary or 

 2-3 together, are produced laterally from the same 

 outgrowth as, but below, the antheridia (Fig. 16 i, p. 44). 



In Tolypella the antheridia are also solitary, but, 

 as well as the oogonia which are usually clustered, 

 are produced as lateral outgrowths and the stalk-cells 

 are frequently elongated (Fig. 16 ii, p. 44). 



In the Gharese the antheridia are not infrequently 

 two together at a branchlet-node and in all the genera 

 are lateral. 



