Tilden: PIL1NIA AND STIGEOCLONIUM. 609 



four nearly cubical portions (PI. XXXII, fig. 1). In a day or two 

 lower cells showed evidence of a similar division and a swell- 

 ing of these cells was also apparent (fig. 7). This behavior 

 proved to be preliminary to the production of megazoospores. 

 It is thus seen that the vegetative cell in becoming a gonidan- 

 gium practically does not change in form. 



The gonidangia develop from terminal cells or from any of the 

 upper cells of the main filaments or the branches. In rare 

 cases they were seen in direct proximity to the basal cell. In- 

 stances occurred in which a short, one-celled reproductive 

 branch sprang off at right angles to the filament. Sometimes it 

 rose from the upper portion of the cell following the ordinary 

 method of branching among the Chaetophoraceae (PI. XXXII, 

 fig. 8), but as often it was developed from the base of the cell 

 (PL XXXII, fig. 9). 



As the spores mature and escape they are found to number 

 from one to four in a cell (PI. XXXII, figs. 10, 11, 13). Cells in the 

 upper branches give rise to two or four zoospores of exactly 

 the same size and appearance. All the other cells in the vicinity 

 of a reproductive cell may be vegetative, some even in the act of 

 sending off branches (PI. XXXII, fig. 13), or several neighbor- 

 ing cells may also be reproductive (PI. XXXII, figs. 7, 12, 14). 



Sometimes the gonidangium is large and roomy (PL XXXII, 

 figs. 14, 15), at other times the spores are crowded together like 

 those of Ulothrix zonata ( PL XXXII, figs. 12, 16 ). Taking an ex- 

 ample of the first sort (PL XXXII, fig. 15), the cell is 16 mic. in 

 length, 4.8 mic. in diameter at the end walls, and 9.6 mic. across 

 the swollen middle portion. The two spores,6.5 mic. in diame- 

 ter, lie easily side by side. An example lowing the contrary 

 condition (PL XXXII, fig. 16) is a cell lLzmic. in diameter and 

 8 mic. in length. The spores like the last are 6. 5 mic. in diameter 

 and they so completely fill the mother cell that the walls are con- 

 siderably distended. A swollen cell containing but one spore is 

 shown (PL XXXII, fig. 10) in the end of a branch all the cells 

 of which are reproductive. 



For some time before escaping, the spores appear perfectly 

 mature. The shape is distinct, either globose or oval accord- 

 ing as the end or side is presented to view. The pigment spot 

 is relatively large and bright. A branch of reproductive cells, 

 the zoospores of which are near maturity and all at the same 

 stage, shows the eye-spots very distinctly (PL XXXII, fig. 12 ). 

 The spores as viewed within the cell appear to have a distinctly 



