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1907] CHRISTMAN— MORPHOLOGY OF THE RUSTS 89 



in the method of formation of the basal cells and in the binucleated 

 condition of the vegetative mycelial cells from which they arise. The 

 primary uredosorus arises from a mycelium of uninucleatcd cells 

 (fiS' 6)} while the secondary uredosorus arises on a mycelium with 

 regularly binucleated cells {fig, i; compare jigs, ip and 21). 



Like the secondary uredospores of Phragmidium potentillae cana- 

 densisy the uredospores of the Coleosporiums are borne upon a myce- 

 lium of binucleated cells. On this mycelium large basal cells are 

 formed in the same way as in Phragmidium. When the spores 

 form, however, as figured and described by Holden and Harper (4), 

 the second uredospore-initial cell is cut off directly beneath the first 

 spore and intercalary cell. This is repeated in the case of the follow- 

 ing spores^ and a row of uredospores separated by intercalary cells is 

 formed, having exactly the appearance of the rows in the true aecid- 

 ium {fig, 20). 



Uredospores are generally unicellular, but, as Roze (24) and later 

 Jacky (15) have show^n, the uredospores of Puccinia chrysanthemi 



^ are quite commonly two-celled. 



teleutospores 



I have studied in detail the formation of the teleutospores of 

 Puccinia podophylli S., and a similar series of cell phenomena to 

 those described for the secondary uredosporc of Phragmidium poten^ 

 tillae canadensis is to be observed here. A series of large binucleated 

 cells is formed beneath the epidermis of the host. These cells are 



w 



the ends of hyphae which are made up entirely of binucleated cells 

 and are in position and general appearance exactly like the basal 

 cells of the uredosori, and like those cells bear the spores. Conju- 

 gate nuclear division followed by cell division now separates off a 

 large distal cell or teleutospore-initial cell {-fig, 7). As in the case of 

 the uredospore, this cell now divides to form the spore and the stalk 

 {f'S^ ^)- In the genus Uromyces the teleutospore remains unicellular. 

 Here, however, like the uredospore of Puccinia chrysanthemi^ this 

 one cell divides to form the characteristic two-celled spore of the 

 genus Puccinia, As is w^ell known in Triphragmium and Phrag- 

 midium, three and four-celled spores are produced from a single 

 im'tial spore-cell. It is plain that this multiplication of cells in the 



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