58 



COMPOUND ORGANS OF PLANTS. 



have represented, a, spore of Conferva glomerata ; b, Pi'olifera 

 rivularis ; c, Vaucheria ungerii, after Thuret. 



66. In plants composed of a cell or a single row of cells, 

 even at this stage of vegetation, a process of great physiologi- 

 cal importance is observed, the evident equivalent of bi-sexu- 

 ality in the higher orders. In Zygnema and other Confervas, 

 which consist of plants composed of rows of cells, the cells, at 

 a certain period, bud out laterally, and coming in contact with 

 similar buds on contiguous filaments, the septa become ab- 

 sorbed, a free communication is opened between the cells of 

 the two filaments, the contents of one cell then pass into the 

 other, and the result is the production of the germinating 

 spore. The common fresh-water plant, called the Hydro- 

 dicton utrioulatum or water-net, is composed of filaments 

 which have united in this manner, and in this case with so 

 much geometrical regularity as to give the plant the appear- 

 ance of a green net, inclosing hexagonal and pentagonal spaces. 

 The process is termed conjugation. In Fig. 24, o, we have a 

 Fig. 24. 



