692 Journal of Agricultural Research voi.xx, No. 9 



chium, in contradistinction to the innate form of the acervnlus which has no such 

 base. The tubercular swelling, due to the massing of mycelium below and in the 

 epidermis, partakes of sporodochial character also, and while this subepidermal part 

 may not be regarded as constituting a true sporodochium it serves to emphasize the 

 tendency of the fungus to produce such structures. . .The structure is a tubercle with 

 a differentiated cortical outer layer. This outer layer ruptures and the tubercle 

 develops as a sporodochium.. .These facts exlcude the fungus from Vermicularia and 

 place it in the Tuberculariaceae under Volutella. 



In the discussion later in this paper on the relation of the parasite to 

 the host it is shown that the development of the fungus commonly begins 

 in the outer wall of the epidermal layer of host cells. As the cellulose 

 becomes softened the hyphae multiply and a definite stroma forms with- 

 in this softened cell wall. Mycelium penetrates the epidermal and 

 underlying cells, and if humid conditions prevail the stroma will soon 

 occupy several layers of subepidermal cells. In good storage this process 

 is comparatively slow, but during a protracted period, especially if the 

 humidity rises considerably from time to time, the stroma commonly 

 does acquire a thickness of several hundred microns. An examination of 

 many sections has shown that regardless of the extent of its development 

 the stroma is always covered by the cuticle of the host. At the instant of 

 sporulation a palisade layer of hyaline hyphae interspersed with dark- 

 colored setae arises from the stroma, and in this process the cuticle is rup- 

 tured. This is shown to occur on stromata of widely different ages in 

 figure 1 and Plate 83, B. It is to be noted in the first illustration that the 

 stroma is of recent development, that it is confined to the outer wall of 

 the epidermal layer, and that the cuticle has been ruptured only by the 

 formation of the acervulus. In the second illustration, although the 

 stroma is much greater in extent, the host cuticle is still to be found in- 

 tact except where it has been ruptured by the two acervuli. 



As pointed out by Saccardo (24, v. 3, p. 221-222, 233), certain species of 

 Vermicularia are characterized by imperfect or cup-shaped pycnidia, and 

 such forms approach the genus Colletotrichum. Obviously it is often dif- 

 ficult to determine the exact nature of the fruiting bodies, and as a result 

 many forms belonging in Colletotrichum have been placed in Vermicu- 

 laria. In the form under consideration there is no suggestion of pycnidial 

 development at any time during the development, of the fruiting body. 

 On the other hand, it does fall within the limits of the genus Colletotri- 

 chum. It is true that the basal stroma is much more highly developed 

 than in many of the better-known species of this genus. However, well- 

 developed stromata have been described in several species of this genus, 

 including Colletotrichum antirrhini by Stewart (31) and C. cereale by 

 Selby and Manns (27). In both cases the stroma develops beneath 

 the cuticle, which is ruptured only upon the formation of the acervulus. 



It is quite possible that a critical study of the closely related species 

 classified at present in Vermicularia and Colletotrichum will lead to the 

 separation into another genus of those forms which develop acervuli above 



