634 MINNESOTA BOTANICAL STUDIES. 



Fig. 3. Filament showing general aspect of plant with characteristic 

 morle of branching. (X 29). 



Fig. 4. Group of short, branch-bearing cells in detail. (X 300). 



Fig. 5. Cells with five spores having pigment spots facing in same di- 

 rection. (X 300). 



Fig. 6. Megazoospores moving actively in the cells thereby causing the 

 walls to become distended. (X 300). 



Fig. 7. Showing spores in early stages of development. (X 300). 



Fig. 8. Spores lying with their longest diameter crosswise of the fila- 

 ment. (X 300). 



Fig. 9. A cell through the end wall of which the spores escaped passing 

 out through a second cell. (X 300). 



Fig. 10. Cell containing zoospores in motion the wall irregularly dis- 

 tended according as the spores changed their position. (X 300). 



Fig. 11. Detached branch of Pilinia thallus, showing one branchlet un- 

 dergoing transformation into Palmella state. (X 300). 



Fig. 12, 13. Vegetative cells in the act of developing into Palmella cells. 

 (X 300). 



Plate XXXIV. 



Fig. 1. Further transformation of cells shown in Plate III, fig. 13. 

 (X 300;. 



Fig. 2. Isolated cells becoming connected by means of the thick gela- 

 tinous coatings. (X 300). 



Fig. 3. Isolated cells dividing into two and four parts, a. Division of 

 contents into two portions accompanied by the separation of 

 the pyrenoid. b. Division into four portions of contents and 

 pyrenoids. (X 300). 



Fig. 4. Plate cell developing zoospores. (X 300). 



Fig. 5. Microzoospores. (X 300). 



Fig. 6. Zygotes. (X 300). 



Fig. 7. Megazoospores of Stigeoclonium. 



The following are all developmental stages of megazoospores 

 forming thalli: 



Fig. 8. Spore in the act of withdrawing cilia. 



Fig. 9. Spores showing pigment spot in posterior portion due .to the 

 elongation of hyaline end. 



Fig. 10. Further growth accompanied by division into two cells. 



Fig. 11. Showing recent division with pyrenoids lying close together on 

 opposite sides of the new wall. 



Fig. 12. Division of pyrenoid into two portions preparatory to forma- 

 tion of wall. 



Fig. 13. Filament with hyaline end of spore still visible. 



Fig. 14. Filament of three cells showing the tendency to curve. 



Fig. 15 and 16, 17 and 18, 19 and 20. First appearance of branching. 



Fig. 21. Threeunbranchedfllamentsbecomingconnectedintoonethallus 



Fig. 22 and 23. Showing thallus developed from a single spore. 



Fig. 24. Thallus building up a somewhat circular plate. 



Fig. 25. Two filaments combined into one thallus. Cells very large and 

 cylindrical for the most part, instead of globose. 



Fig. 26. Filament with numerous branches. 



Fig. 27 and 28. Prostrate branches forming upright filaments. 



