MIYABE & TAKAHASIII: rEROXOI'lASMOPAKA HUMULI. jrj 



int,^ formed at the apical papilla. The zoospores are kidney-shaped with two cilia 

 attached to its lateral side. 



The oospores are formed in abundance in the mesophyll of the discolored spots. 

 They are spherical, smooth, 28-34 /' in diameter, and light brownish in color. 

 The wall of the oogonium is persistent and loosely surrounding the oospore. The 

 diameter of the oogonium is about 40 n. 



This fungus with its dichotomously branched conidiophores and with its 

 conidia germinating b}- zoospores shares the characters of two genera Pcronospora 

 and Plasvwpara, and may form an intermediate genus together with the downy 

 mildew fungi of cucumber and Celt is. In 1901, Bei'lese' created a new subgenus, 

 Pcronoplasviopara, in the genus Plasviopara and placed under it Peronospora 

 cubcnsis Berk, et Curt, and Peronospora Celtidis Waite. Rostowzew- reported in 

 1903 a detailed account of his study on different species of the Peronosporaceae, 

 but especially on Peronospora cjtbensis 13. et C. on which he founded a new genus 

 Psciidoperonosporo, apparently without knowing the above mentioned work of 

 Berlese. 



In 1904. Clinton'^ made a critical study of the cucumber mildew and came to 

 a similar conclusion in regard to the recognition of its generic position. But re- 

 garding Berlese's subgenus. Pcronoplasviopara, because of priorit)' of publication, 

 and also because it was given definite descri])tive characters, as deserving prefer- 

 ence over RostOWZew's rather indefinite Pscudoperonospora, Clinton ele\-ated 

 Peronoplasnwpara to generic rank and included under it two species, — Peronoplas- 

 viopara ciibensis (B. et C.) Clint., and Peronoplasmopara Celtidis (Waite) Clint. 



In the present paper, w^e have adapted Clinton's view and named our fungus 

 Peronoplasmopara Huviuli ]\Iyb. et Tak., thus adding another species to this in- 

 teresting genus. 



In this connection, it may be interesting to know, that Peronosplasmopara 

 Celtidis is also found in Japan on Celtis si)iensis. It was collected by Mr. K. 

 Yoshino in the Province of t^chigo in 1903. The specimen was sent to one of us 

 for determination, and it was proved to correspond exactly with the descriptions 

 and figures o'i Peronospora Celtidis Waite. ^ 



An apparently rare species Peronospora eannabina Otth parasitic on the leaves 



1. Beriese, A. N. Plaimopara iiihcmis (B. et C-). Riv. Pat. Veg. \o\. 9. p. 123-6. 1901. 



2. Rostowzew, S. J., Beiträge zur Kenntnis der Peronosporeen. Flora. Bd. 92. p. 405-430. 1903. 



3. Clinton, G. P., Downy mildew, or Blight, Peronoplasmopara cubcmis (B. & C-) Clint., of Musk 

 Melons and Cucumbers. Report of the Conn. Agric. Exp. Stat, for the Year 1904. p. 329-362. 1905. 



4. Waite, M. B., Description of Two New Species of Peronospora. Journ. of Mycology. Vol. VII. p. 

 105-109. Pi. XVIII. 1892. 



