Apr. 8, 1918 



Relation of Soil Fungi to Potato Diseases 



95 



slow development of colored fruit from the center outward, surface growth from 

 velvety at the margin with center floccose to floccose out to the very edge of the 

 colony, some strains zonate, reverse of colony at first colorless, in some strains remain- 

 ing so, in others developing colors, a succession of colors appearing in series so that 

 different strains become finally yellow, orange, orange -red, rosy, or even deep-red ; 

 the color mostly remains in the mycelium; hence, does not discolor the agar beyond 

 the areas of immediate contact, if at all. 



Odor produced, none or indefinite. 



Conidiophores either rising directly from the substratum or as branches of aerial 

 hyphae, from very short up to 1,000 m in length, or longer, slender mostly, 2 to 3 

 occasionally up to 4 m in diameter, with walls smooth in some strains, slightly granular 

 or roughened in others, or showing both conditions in the same culture; conidial 

 fructifications variously branched from a single terminal verticil of sterigmata (coni- 

 diferous cells) to a verticil of metulae (branches bearing verticils of sterigmata) 

 including the main stalk prolonged and a single branch or a whorl of branches, more 





Fig. 4. — Penidllium soil series (strain 2490)! Colonies differing very little in structure from strain 89 (fig. 3), 

 but with reverse colors slowly yellow to orange. Drawn by Dr. Charles Thom. 



rarely twice verticillate or partly so-, sterigmata few in each verticil, mostly slender 

 7 to 10 by 2 to 2.5 M. narrowing to a slender tube from which the conidia are formed. 

 Conidia at first definitely elliptical, i to 2 by 2.5 m, at first becoming 2.5 /n in diameter 

 or even 3 to 3.5 m in age, continuing elliptical or becoming almost globose, either 

 smooth or delicately roughened or both conditions in the same strain (fig. 3,4). 

 Habitat: Soils. 



PERICONIA 



Periconia byssoides Pers. 



Isolated four times from Idaho soils, once from sample 3, once from 

 group A, and twice from group B. Identified by Mr. Zundel. 



RHIZOPUS 



Rhizopus nigricans Ehr. 



Isolated once from group C. Identified by Mr. Zundel. 



