BOTANICAL GAZETTE 309 



PHYTOPHTHORA DeBary. 



Conidia at first solitary and terminal, but beaming lateral by the outgrowth of the 

 tip of the conidiophore. Several conidia produced in succession. Germination by 

 zoospores. 



Ph. infestans (Mont.) DeBary. Potato Rot. 



Botrytis infestans Mont., Bot. devastatrix Lib., Peronospora devastatrix Casp., Per 



onospora infestans Casp., DeBary et al. 

 Exs. Myeotheca Universalis no. 926. , 



Mycelium slender, without haustoria. Conidiophores simple 

 or with a few irregularly placed branches, attenuated at the apex, 

 with one or more nodosities below at the insertion of the conidia. 

 Conidia ellipsoid or oval with a terminal papilla. Oospores? 1 



Common on cultivated potatoes from Maine to California (Harkness), and 

 on tomatoes to South Carolina (Kavenel). Europe. 



PERONOSPORA Corda. 



Conidiophores variously branched or mrcly simple, conidia always terminal. Ger- 

 mination either by zoospores or outgrowing tubes. 



Section I. Zoosporipar.e. Conidiophores pinnately branching, ultimate 

 divisions often glomerate. Germination by zoospores. 



1. P. viticol\ (Berk. & Curt.) DeBary. 



Botrytis cana Schw. in Herb. Sehweinitz non B. cana Lk. 

 Botr. viticola Berk. Crypt. Bot. 301 ; 23d Rept. N. Y. Bot. 61. 



Per. viticola DeBary Ann. Sci. Nat. 4 Ser. T. XX. 121 ; Bull. Bussey Inst. I. -VI, ; 



Grevillealll.iOH, VI. 139. Bull. 111. Mus. I. p. 55, pi. II. 687. 

 Exs. Myeotheca Universalis 617; Ellis North Am. Fung- 208; Ravenel Fung. 



Car. V. 60; Fung. Amer. 01. . 



Mycelium varicose, haustoria small, spherical. Conidiophores 

 with a long, slender main axis, with a few short, subequal, alter- 

 nate, horizontal 1 to 3 pinnate branches at the top. Tips acute, 

 densely clustered in sets of usually three. Conidia small, ovoid- 

 obtuse, average 17-23// by 13-17//.. Oospores about 30-38//-, 

 rather thin walled, yellowish, exospore smooth or slightly 

 wrinkled. 



Common on wild and cultivated grapes east of the Rocky Mts. Europe. 

 Algiers. Appearing with us in midsummer and autumn. 



Note— Since the introduction of our grape mould into Europe an im- 

 mense amount has been written on its progress and prevention. In this con- 

 nection the reader is referred to the latest work on the subject: Le. Peronospora 

 des Vignes, by Dr. Max. Cornu. 1882, in which the bibliography is very fully 

 given with admirable plates of the fungus. 



ir rhe oospores of this species are unknown to DeBary. Mr. Worthington 

 G. Smith, in Gardener's Chronicle, July 17, 1875, and Quart. Journ. Micros. 

 Sci., Octobor, 1875, reported the discovery of oospores, and in the last named 

 journal gave photographic copies of his preparation. The discussion which 

 took place on this subject has frequently been quoted in American journals, 

 and those who wish to examine the question more fully should consult DeBary s 

 Researches into the nature of the Potato Fungus, Jour. Royal Agric. Soc. of Eng- 

 land, and the two papers of Mr. Smith previously mentioned. 



