Fusaria of Potatoes 115 



the conidia are borne singly and remain thus in. the form of a powder. 

 Usually, however, they adhere to the tips of conidiophores for a time, 

 forming balls of variable size. This may be the case with microconidia 

 as well as with macroconidia. In certain Fusaria, such as F. cuneiforme, 

 and in all members of the section Martiella, these balls of conidia are 

 especially prominent; but they are very common also in the other Fusaria 

 and therefore cannot be used for specific differentiation. 



When there is no room for old conidia to be pushed aside — that is, 

 when the fruiting branches are very numerous and close together - — 

 a considerable and continuous mass of spores results; these, when the air 

 is moist, form a roundish, wartlike heap of spores, which, with the 

 conidiophores producing them, is known as a sporodochium. When 

 the air is comparatively dry, the spores are pushed up in more or less 

 curled, long, tendril-like columns. This is often observed especially 

 in many cultures on sterilized canes of red raspberry and in stem plugs 

 of other plants. 



Often small sporodochia are produced on and strewn all over the aerial 

 mycelium, producing a picture very characteristic for F. subulatum and 

 some other Fusaria. In other cases minute and numerous sporodochia 

 are produced very close to or on the surface of the substratum, and when 

 these minute sporodochia are very numerous they form a nearly con- 

 tinuous, slimy layer of conidia. The fructification then resembles a 

 pionnotes and is called here pseudopionnotes. In one case a seemingly 

 true pionnotes 29 — that is, a thick, continuous, slimy layer of spores — 

 was observed (in F. udum var. Solani). A pseudopionnotes may be 

 produced under aerial mycelium which may more or less mask its macro- 

 scopic appearance, as in the case of several Fusaria of the section Elegans; 

 but in certain cases there is no aerial mycelium over it, and the pseudopion- 

 notes remains fully exposed and characteristic for certain species. (See 

 F. metacroum, F. jalcatum, and F. discolor var. sulphur eum.) 



Mycelial threads in many Fusaria often run parallel and anastomose 

 more or less closely, thus producing a ropelike structure which may come 

 up into the air in an irregular fashion and which also may bear more 

 or. less abundant conidia produced on side branches. These ropelike 

 structures then resemble coremia, which are columnar fruiting bodies, 

 typical of the family Stilbaceae. No true coremia were observed in 

 any of the Fusaria presented here. 



"The definition is taken from Lindau (1908-1909 : 509). 



