616 MINNESOTA BOTANICAL STUDIES. 



vegetative cells. In one detached filament, the reproductive por- 

 tion extended for a distance of 675 mic, then came a few vege- 

 tative cells and lastly the bristle. The spores were quite 

 mature, but seemed most so at the middle of the reproductive 

 area, as some here had already escaped from the cells. 



One branchlet from a group was prolonged far beyond its 

 fellows and consisted of a row of reproductive cells 125 mic. in 

 length at the end of which were several vegetative cells not 

 yet changed into gonidangia, and the whole terminated by a 

 bristle, 350 mic. in length. 



The reproductive cells contain from 1-16 megazoospores each. 

 The spores soon showed a large pyrenoid and a distinct eyespot. 

 In a detached end of a filament consisting of three cells the 

 contents of each cell was divided into two portions which were to 

 become zoospores. The pigment spots of the four spores 

 nearest the end and also the sixth one were situated on the same 

 side (PI. XXXIII, fig. 5). The fifth pigment spot was on the oppo- 

 site side. Without exception the large pyrenoids were on the 

 same side of the filament. In another case, two cells of a branch 

 had each two pigment spots facing in the same direction and 

 one cell had two pigment spots facing in opposite directions. 

 Still another branch had cells containing two or four spores 

 each; for the most part the pigment spots alternated. 



The megazoospores measure from 5-7.5 mic. in diameter and 

 are from 10-12 mic. in length. In shape they are broadly 

 elliptical or egg-shaped. In general their longest axis lay 

 transverse to the filament. Occasionally they lay with their long- 

 est diameter parallel with the filament (PI. XXXIII, fig. 8). 



It is interesting to watch the process of evacuation of the goni- 

 dangium. For this purpose a certain cell was kept under obser- 

 vation (PI. XXXIII, fig. 6). The spores were eight in number 

 and had reached a point where they were distinctly separated 

 from each other and were already evincing a slight activity. This 

 soon gave place to a very energetic movement. Thus each 

 individual spore began a series of almost imperceptible little 

 jerks. These constantly grew stronger until they became to 

 and fro movements in the cell. Finally, all the spores were 

 darting hither and thither in the cell in all directions, around 

 and over each other. Meanwhile the walls of the cell seemed 

 to have become somewhat gelatinized. The force used by the 

 spores in striking against the sides resulted in the walls being 

 stretched out or swollen so that the cell became barrel-shaped 

 in outline. 



