220 AGRICULTUEAL EXPERIMENT STATION. [Jan. 



slimy mass of decay, while a neighboring one, sown with 

 spores in pure water at the same time, remained perfectly 

 sound. Two days later the whole plant had succumbed. 

 If a bit of decayed tissue, containing abundant and vigorous 

 threads of the fungus, be placed upon a healthy plant, the 

 latter is promptly attacked and destroyed. These results 

 furnish interesting confirmation of DeBary's conclusion* that 

 the spores of this fungus are unalile to attack its host-plants 

 parasitically until their germ tul)es have been saprophyti- 

 cally nourished for a time. That is, the fungus may be said 

 to be in process of acquiring a truly parasitic habit which it 

 has not yet fully develo})ed. There is no reason to d()ul)t 

 that these spores, germinating on the rich soil of the green- 

 house, al)out the bases of the plants, find there all the 

 nourishment needed for the development of a mycelium 

 ca[)able of parasitic invasion. It seems very probable, too, 

 that DeBary's explanation* of the significance and function 

 of the so-called attachment organs is the correct one. This 

 is to the effect that these organs, developed on the firm 

 surface of the host from the saprophytically nourished my- 

 celium, produce in the fluid which results from the breaking 

 down of their protoplasm, previously described, some sub- 

 stance which softens the cell walls and kills the cell contents 

 of the host. The fungus-threads are then able to attack 

 these dead cells, and thence to penetrate farther and farther 

 into the tissues of the host-plant. After its establishment, 

 and the development of an al)undant mycelium within the 

 host, the fungus forms its sclerotia just as in the cultures 

 above described, their form being somewhat modified by the 

 shape of the cavity when they develop in the inner spaces 

 of the plant. 



Wo pass now to consider the question of other spore 

 foi'ius of this fungus. It is a well-known fact that many 

 Ascomycetous fungi possess one or more secondary "sum- 

 mer spore " forms, known as conidia, pycnidia, etc. ; and 

 some such forms have been found to belong to those si)ecies 

 of fungi most closely related to the })rcsent one. None has, 

 however, been heretofore proved to belong to the present 

 species. Therefore, when, in examining plants in Mr. Raw- 



* Bolanische Zeitung, 1886, Nog. 22-27. 



