110 Wisconsin Academij of Sciences^ Arts and Letters, 



25. Peronospora australis Spegaz. (P. sicyicola Trelease, Botrytis 

 cubensis B. & C ? ). 



Very abundant in summer and fall, on Sicyos angulatus L. Madi- 

 son, Stoughton. 



This species was fir^t found in the summer of 1882. Its presence is indi- 

 cated by pale spots on the upper surface of the leaf, opposite which the 

 fruiting hyphae ecuerge in dense white tufts 1-3 mm. in diameter, with an- 

 gular contour, limited by the veinlets of the leaf. Later these spots be- 

 come dead and white, resembling those caused hj Ramularia, Sej^toria, etc. 



Berkeley and Curtis describe a Peronospora cubensis on a West Indian 

 cucurbitaceoHS plant (Journ. Linn. Soc, Bot., X., 363), but their description, 

 like many of Berkeley's, is unsatisfactory and does not well apply to our 

 plant. Through the courtesy of Dr. Farlow, I have made a thorough ex- 

 amination of the leaf said to bear Botrytis cubensis, in the Curtis herbar- 

 ium, but whatever it may have once contained has entirely disappeared; 

 and a careful search on the Wright duplicates at Cambridge, which Dr. 

 Farlow was kind enough to make, does not show any Peronosx^ora. The 

 species was, therefore, named P. sicyicola in my herbarium and in this pa- 

 per as first presented, and a description was given by Dr. Farlow, in the 

 Botanical Gazette for 1883, p. 331. Since that was published the descrip- 

 tion of a South American species on Cyclanthera, discovered by Spegaz- 

 zini, has reached this country. So far as can be made out, this is identi- 

 cal with the Wisconsin form, and the name of Spegazzini has the right of 

 priority, dating from 1881. His description is as follows: "Hypophylla; 

 maculae amphigenae, magnitudine ludentes, primo . parvulae, dein saepe 

 totum folium occupantes, pallescentes v. fusco-pellucidescentes, angulosae; 

 hyphae mycelii crassae, subtorulosae: haustoria subsphaeroidea v. subcla- 

 vata, numerosa, saepe totam cellulam plantae hospitalis implectantia; hy- 

 phae f ertiles hinc inde erumpentes v. e stomatibus exsurgentes, rectae-cylin- 

 draceae, longiusculae (250 — 500X14 — 15//), hinc inde glomeruJatae, usque ad 

 verticem continuae, inferue saepe incrassatulae, sed mox breviter ac abrupte 

 coarctato-attenuate, apice subverticillatim 5 — 12 ramosae; rami 3 — 6- 

 ies trichotomi, gradatim alternati, a^ abbreviati; ramuli ultimi apice in- 

 crassatuli, 3—5 sterigmata (3.5X1-5 — 3 /*) hyalina, &ubamiDulliformia, inter 

 se angulo-recto divergentia, saepe 2-3 denticulato-lobata gerentia; cooidia 

 obovato-sphaeroidea, sursum obtuse rotundata, saepeque apiculata (15 X 1 — 

 12//), hyalina.'" — Ann. dela Sociedad Cientif. Argentina, 1881, XII., p. 81. 



In our form the conidial bi'anches are hyaline, tufted from the stooiata, 

 often .5 mm. high, with a diameter of 12 jn- 3-4 times branched below. Pri- 

 mary branches alternate, ascending. Ultimate and often penultimate twig^ 

 spreading, the lateral ones in pairs, forming crosses with the branch Avhich 

 bears them. Conidia hyaline, sub?pherical or broadly ellipsoidal, variable 

 iu size, averaging 13x16 /<; with an apical papi'la, hence probably ger- 

 minating by zoospores. Oospores not seen. 



