39 8 FUNGOUS DISEASES OF PLANTS 



LMib vitlgaris, Vigna marginata, etc. The fungus commonly 

 appears late in the season, and it is often destructive to foliage, 

 causing early maturity and lessened production of the beans. There 

 is great difference in susceptibility of varieties both among dwarf 

 and pole sorts. Moreover, the fungus is harbored by the old leaves 

 and vines. Burning these would reduce the quantity another year. 

 The effect of turning under affected parts does not seem to have 

 been tested. Selection of resistant varieties would seem to be 

 possible for each locality. The spermogonia and aecidia are very 

 light in color. The aecidiospores are colorless and polyhedral, 

 17-32 x 14-23/1; the obovate, minutely echinulate uredospores, 

 which are 24-33 X 16-20 /JL, occur in rather minute sori ; and the 

 teleutospores are broadly elliptical, measuring 26-35 X 20-26/1, 

 and each spore is provided with a large, terminal papilla. 



VI. RUST OF VETCH AND GARDEN PEA 

 Uromyces Pisi (Pers.) De Bary 



DE BARY, A. Recherches sur le deVeloppement de quelques champignons 



parasites. Ann. d. Sci. nat. Bot. (Sdr. 4) 20: 68-99. l ^3- 

 KLKBAHN, H. Die wirtswechselden Rostpilze, I.e., p. 330. 



In the United States this species is not so prevalent as the pre- 

 ceding species. It shows, however, an interesting heteroecism. The 

 pycnidia and aecidia occur on Euphorbia Cyparissias, while the 

 uredospores and teleutospores are found upon Lathyrus pratensis, 

 Vicia cracca, Pisnm sativum, and Pisum arvcnse. In addition, a 

 number of other hosts have been given for stages II and III. In 

 this rust the aecidia and spermogonia are together irregularly dis- 

 tributed on the under surfaces of the leaves. The aecidia are 

 numerous, with deeply cleft peridia, the cells of which have a very 

 slight lumen. The aecidiospores are more or less isodiametric, and 

 from 1 8 to 22 /i in diameter. The spore wall is decorated with fine 

 wart-like projections. The uredosori are small, pulverulent, and 

 distributed over the leaf. The uredospores are more or less spher- 

 ical, and measure 21-25 M- The wall is thick and the 4-5 germ 

 pores arc evident. The teleutospores are obovate, with short, hya- 

 line stalks. The wall is uniformly thickened and beset with fine 

 warts, except at the apex, where there is a conspicuous, flat papilla. 



