1907] CHRISTMAN— MORPHOLOGY OF THE RUSTS lOi 



Figs. 13-16. — ^Various stages of nuclear migration in the m}'celium of the 

 teleutosorus. 



Fig. 17. — ^A mycelial cell showing three nuclei. 



Semi-diagrammatic figures 



Fig. 18. — Phragmidium speciosum. Mycelial cells of the aecidium showing 



uninucleated cells bearing a fusion cell and the rows of spores and intercalary cells. 



I Fig. 19. — Phragmidium poientillae canadensis, showing uninucleated mycelial 



cells in the primary uredo similar to those in the aecidium; a fusion cell is formed 

 in much the same way as in the aecidium; the elongated basal cell represents an 

 outgrowth after fusion; here the spores are budded off as a horizontal series 

 and are borne on stalks. 



Fig. 20. — Coleosporium solidaginis. Uredospores borne in chains on a 

 mycelium of binucleated cells. 



Fig. 21. — Phragmidium potentillae canadensis. Secondary uredospores 

 budded from the basal cell; the mycelium is composed of binucleated cells. 



Fig. 22. — -Puccinia podophylli. Teleutospores in various stages of forma- 

 tion; the cells of the mycelium each contain two nucleic 



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