Feb. i, 1921 Onion Smudge 693 



thick basal stromata. This question, however, is not within the province 

 of the present paper. Those species of the Hyphales which are placed in 

 the family Tuberculariaceae are characterized by the grouping together 

 of the sporif erous hyphae in a superficial, conglutinate, sessile, or stipitate 

 mass, known as a sporodochium (24, v. 4, p. 635, 682). As already pointed 

 out, Stevens and True (jo) considered the fruiting body of the onion 

 smudge organism to be of this nature and on that basis have transferred 

 it to Volutella. In their description and figures, however, they seem to 

 have interpreted the host cuticle as part of the so-called tubercle and 

 thus as being of fungus origin. Were this true, the stroma would be super- 

 ficial, and the fungus would properly belong to the genus Volutella. 

 However, since the stroma is always subcuticular and the sporiferous 

 hyphae are subcuticular in origin, the form is more characteristic of Colle- 

 totrichum than of Volutella. Here again it is obvious that these two 

 genera need more critical study before their limits can be satisfactorily 

 denned. Meanwhile in the light of evidence just given, the writer con- 

 siders it more suitable to use the name Colletotrichum circinans (Berk.) 

 Voglino for the onion smudge organism. 



The comparison of Colletotrichum circinans with other related species 

 has been very limited in this investigation. The list of species of this 

 genus which coincide closely with the one in question as to spore meas- 

 urements and general characters is large and extends over a wide host 

 range. Obviously the comparison of herbarium specimens is insufficient 

 basis for final conclusions under the circumstances. Critical comparison 

 has been confined to C. jructus (S. and H.) Sacc, described as causing a 

 fruit rot of apple. This species was originally described as a species of 

 Volutella (28), but it was later transferred to Colletotrichum by Saccardo 

 {24, v. 13, p. 1201)— 

 on account of the black setae and the acervulus being originally subcuticular. 



Cross sections of apple fruits affected with C. jructus and with C. circinans 

 are compared in Plate 83, C, D. In both cases the development of the 

 stroma beneath the cuticle, which is ruptured only upon the formation 

 of the acervuli, is clearly shown. The former species was chosen for com- 

 parative study because the spore measurements and general characters 

 as previously described were closely similar to those of the onion smudge 

 organism and authentic cultures were available. 



Cultures of the apple organism or diseased fruits were secured from 

 Prof. C. R. Orton, State College, Pa., Dr. L. R. Hesler, Ithaca, N. Y., Dr. 

 Charles Brooks, Washington, D. C, and Mr. G. A. Meckstroth, Columbus, 

 Ohio. Cross inoculation on apple and onion showed that Colletotrichum 

 circinans was able to produce a rot of apple fruit similar to that produced 

 by C. jructus (see Pi. 84, C). The formation of stromata and acervuli by 

 both species on apple is shown in Plate 83, C, D. The rate at which the 

 rot progressed, however, was uniformly slower in C. circinans. On onion, 



