220 AGRICULTURAL 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 l)it of deca^'ed 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 unable to attack its host-plants 

 parasitically until their germ tu])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 developed. There is no reason to doubt 

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

 house, about the bases of the plants, find there all the 

 nourishment needed for the development of a mycelium 

 capable of parasitic invasion. It seems very prolialde, 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 alile 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 abundant 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 i)lant. 



AYe pass now to consider the question of other spore 

 forms 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 species 

 of fungi most closely related to the ])resent one. None has, 

 however, been heretofore proved to belong to the present 

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



* Botanische Zeitung, 1886, Nos. 22-27. 



