THE FUNGI WHICH CAUSE PLANT DISEASE 335 



of which the telial stage is not yet known. It becomes neces- 

 sary for the present, for convenience of reference, to have 

 names by which to designate these forms. For this purpose the 

 form-genera ^Ecidium Caeoma, Peridermium, Roesteha and Uredo 

 are recognized. We group these under the heading Uredinales 

 Impeifecti. 



Darluca and Tuberculina, two imperfect fungi, are often found 

 growing as parasites upon the rust fungi. 



Key to Families of Uredinales 



Teliospores in germination becoming 

 4-celled, compacted laterally 

 into waxy layers; walls of the 



spores weakly gelatinous 1. Coleosporiacese, p. 335. 



Teliospores germinating by a promy- 



celium 



Teliospores compacted laterally 



into a crust or column (rarely 



solitary within the tissues); 



walls of the spores firm 2. Melampsoracese, p. 340. 



Teliospores free or fascicled; walls 

 of the spores firm or with an 

 outer hygroscopic layer cov- 

 ered by cuticle 3. Pucciniacese, p. 353. 



Teliospores unknown 4. Uredinales Imperfecti, p. 389. 



Coleosporiacese 



Teliospores united in a one or two-layered waxy cushion, ses- 

 sile or borne on a broad sac-Uke stalk and then at the beginning 

 2-celled. Each original spore-cell divides to four super-imposed 

 cells from each of which a simple sterigma emerges. This bears a 

 large basidiospore. 



The most important character is the peculiar mode of basidio- 

 spore production, the 4-celled promycelium being formed within 

 the spore. 



The family is of little economic importance except in its secial 

 stage on conifers. 



