148 JAMIESON AND WOLLENWEBER : FUSARIUM TRICHOTHECIOIDES 



sporodochium or Pionnotes stage also occurs: Conidia of the for- 

 mer 1-3 septate, medium size, 15-26 x' 4-5 \ microns, formed as a 

 slightly curved comma, ellipsoidally rounded on both sides; 

 conidia of the latter type 3-5 septate, 24-42 x 4^-5| microns; 

 form of the Discolor type. Conidia masses and plectenchyma 

 salmon colored to carrot red when slightly moist, but lighter and 

 usually rosy-white when powdery dry and intermixed with my- 

 celium. Yellowish to brown stromata may be formed. Conidi- 

 ophores of the comma type, mostly irregularly branched, with 

 prominent sterigmata, the arrangement of which is scattered, or 

 especially at the top, trifurcate. Conidiophores in the sporodo- 

 chia more highly developed, like those of F. discolor. Chlamy- 

 dospores seldom occur, and when present are intercalary, in chains 

 or single. 



Causes decay of potato tubers, especially under storage con- 

 ditions. Diseased spots sepia-brown within. The early stage 

 shows a very brownish black discoloration of the layer border- 

 ing the sound tissue. Spokane, Washington; St. Paul, Minne- 

 sota; Dayton, Iowa; Alliance, Nebraska; and Spearfish, South 

 Dakota. 



The two stages of conidial development above mentioned give 

 this fungus an individual place in the genus. Less developed 

 spores of other species may occur under abnormal conditions, but 

 disappear when grown on a favorable host; but F. trichothecioides 

 as a rule produces this smaller form abundantly both in nature 

 and in pure culture. Spores of this stage resemble (Fig. A, E, F) 

 exactly Trichothecium (Link) Corda, described and figured by 

 Corda. 2 The sterigmata of the conidiophores, often trifurcate 

 at the tops (Fig. C), seem to indicate a relationship to Basidiomy- 

 cetes. Most important for the determination of the fungus, how- 

 ever, is the development of the higher type (Fig. B) in pure cul- 

 tures. It forms salmon-colored sporodochia of the well known 

 tubercularia-like type on the surface of sterilized, not too moist 

 grains of cereals and mature stems of plants. The conidiophores 

 of these sporodochia (Fig. D) are verticillately branched and show 



2 Icones fungorum, 1838, p. 10, cum tab., IX, fig. 48, 49. 



