io8 Transactions British Mycological Society. 



of a specific disease, hadromycosis, which is one of that 

 congeries of diseases included under the term "Curl" by older 

 writers. 



Hallier placed his fungus in the genus Rhizoctonia, because 

 he supposed that it produced certain black, pseudo-parenchy- 

 matous bodies (provided with stiff black hairs or setae) which 

 he found on the diseased plants and which he regarded as being 

 sclerotia. There is, however, no proof that these bodies 

 belonged to the fungus luxuriating in the wood vessels, and it 

 is now certain that V. albo-atrum produces no such sclerotia. 



Bodies corresponding to Hallier's sclerotia were very fre- 

 quently met with on dead or dying portions of potato stalks, 

 especiall}^ on the parts below ground, and often in plants 

 attacked by V. albo-atriim. They have not been seen on tubers, 

 although no special search for them there was instituted. 

 They arise beneath the epidermis through which the setae 

 first make their appearance, and one of them in this condition 

 is illustrated in Fig. 6, Plate III. By bursting through, or 

 by the decay of the superficial tissues of the stalk, the whole 

 black body ultimately becomes exposed. The setae are just 

 visible with the naked eye but are somewhat easily broken 

 off on handling the material. Occasionally (when still present) 

 the pith of potato stalks bearing these bodies is of an amethyst 

 tinge. 



In some respects these bodies do resemble sclerotia, and they 

 may perhaps function as such temporarily. When young, at 

 any rate, they appear to contain appreciable quantities of oil. 

 But the walls of the hyphae making up the pseudo-parenchy- 

 matous tissue are not so thick as one comm^only finds in 

 sclerotia. 



For some time I was in doubt as to what these bodies really 

 were. Hence, portions of potato stalks bearing large numbers 

 of them were placed in a moist dish, and kept under observation 

 for a considerable time during the summer of 1915. After a 

 while a moist, amethyst-coloured globule arose on the upper 

 surfaces of a number of the black bodies resembling bacterial 

 colonies, but made up, in reality, of masses of conidia. Sections 

 through the bodies showed that they were solid, and that the 

 conidia were produced from a compact surface layer of conidio- 

 phores. From this surface the setae also arise; their bases 

 are surrounded by the conidiophores and become submerged in 

 the uprising conidial mass, their tops alone protruding above it. 



The structure, as thus revealed, is evidently the fructifying 

 stage of a species of Colletotrichum, and the puzzle as to the 

 nature of what Hallier figured as sclerotia of a Rhizoctonia 

 may now be regarded as solved. A vertical section through 



