[Vol. 2 



416 ANNALS OF T1JE MISSOURI BOTANICAL GARDEN 



tioned, the hyphae constituting the external mantle may be 

 uniformly distributed, as is the case usually when the fungus 

 attacks fleshy roots or tubers, or they may also form a num- 

 ber of aggregates having the appearance of loose or root- 

 like strands. The strands are developed later rather than 

 early in the progress of the disease. They are conspicuous 

 on such hosts as alfalfa and sainfoin. These strands course 

 along the whole root system; they also pass out into the 

 soil, apparently beyond the minutest rootlets, and doubt- 

 less attack plants in the vicinity. Upon the larger strands 

 sclerotia may be formed, and thus the sclerotia are connected 

 with the mantle of hyphae. 



Infection Cushions. — Small stromatic bodies distributed 

 amongst the hyphae were noted by several of the early ob- 

 servers. Kiihn ('58) calls special attention to them on the 

 carrot and the potato. The brothers Tulasne ('62) studied 

 and described them in some detail and came to the conclusion 

 that these were the early stages in the development of the 

 perithecial form. Search for the reproductive phase was in 

 this way transferred from the sclerotium to the bodies in 

 question. Sorauer ( '86*) among others accepted the view of 

 the perithecial nature of this structure. Prillieux ( '91) seems 

 to have been the first to point out that the ' ' corps miliaires, ' ' 

 as he termed them, are in reality special mycelial cushions 

 having the important function of effecting the penetration of 

 the host. He regarded them as the main, if not the sole, seats 

 of tissue invasion, and his studies included a comparison of 

 these bodies and of the penetrating strands in alfalfa, sugar 

 beet, and crocus. After mentioning these cushions as one 

 type of sclerotia, Prunet designates them more specifically as 

 minute "corps noiratres," .2 to 1.2 mm. in diameter with a 

 brown hyphal cortex and a colorless medullar. He indicates 

 that these as well as the larger sclerotia send out filaments 

 which enter the soil and extend the fungus. These bodies 

 have also been figured by Bailey ( '15) in the case of the occur- 

 rence of the fungus on the potato in Oregon and particularly 

 well by Salmon and Crompton ('08, pi. 25). The writer is 

 of the opinion that Prillieux 's notion is in general correct, 



