68 Journal of Agricultural Research voi. v. no. a 



fusely in these two host plants after they mature or are killed by the 

 parasite, but the writer has been unable to find oospores in the young 

 plants during the fall, and this agrees with Magnus's (9) report that 

 oospores are not produced in the seedling plants of spinach infected 

 with Peronospora effusa in the fall. Magnus also states that the same 

 is true in the case of Stellaria media and Veronica hederaefolia infected 

 with Peronospora alsinearum and Peronospora grisea, respectively. 



The number of species of the genus Peronospora that may survive the 

 winter in the mycelial stage are more numerous. Table II shows nine. 

 Careful study is in progress in regard to the remaining species of this 

 genus. As also shown in this table, there are three species of Plasmopara 

 which may survive the winter in this stage, and this number, the writer 

 is confident, will be increased by further studies. 



SUMMARY 



(i) There are at least several species of Peronosporaceae belonging to 

 four genera that may be perennial in the tissues of their hosts, the myce- 

 lium passing the winter either in the aerial or the underground organs of 

 winter annuals, biennials, or perennials. 



(2) Phytophthora infestans is not an exception in the family to which 

 it belongs as regards perennial mycelium. 



(3) The role of the mycelium of Phytophthora infestans in the tubers 

 of its host is not an unusual one. It may grow from the tubers up the 

 stem to the surface of the soil, sporulate, cause foliage infection, and 

 bring about an epidemic of the disease. 



LITERATURE CITED 

 (1) Bary, Anton de. 



1861. Die gegenwartig herrschende KartofFelkrankheit, ihre Ursache und 

 ihre Verhtitung. 75 p., i pi. Leipzig. 

 (2) 



1863. Recherches sur le developpement de quelques champignons parasites. 

 In Ann. Sci. Nat. Bot., s. 4, t. 20, p. 5-148, pi. 1-13. For translation 

 see The potato disease. In Jour. Quekett Micros. Club, no. 22, 

 p. 139-145- 1873. 



(3) 



1876. Researches into the nature of the potato-fungus — Phytophthora infes- 

 tans. In Jour. Roy. Agr. Soc. England, s. 2, v. 12, p. 235-269, 8 fig. 

 Reprinted in Jour. Bot. [London], v. 14 (n. s. v. 5), no. 160, p. 105- 

 126; no. 161, p. 149-154. 



(4) Butler, E. J., and Kulkarni, G. S. 



1913. Colocasiae blight caused by Phytophthora Colocasiae Rac. In Mem. 

 Dept. Agr. India, Bot. Ser., v. 5, no." 5, p. 233-261, pi. 1-4 (i col.). 



(5) IsTVANFFi, Gyula de. 



1904. La perpetuation du mildiou de la vigne. In Compt. Rend. Acad. Sci. 

 [Paris], t. 138, no. 10, p. 643-644. Also in Rev. Vit., t. 21, no. 535, 

 . p. 312. 



