Algae. — Eumycetes. — Pflanzenkrankheiten. 215 



>ium, P. angulosam var. acaneosum, P. integrum, P. Tetras mit var. 

 lithuanica Kol. Echte Planktonformen sind: Elakatothrix gelatinosa 

 Wille, Ankistrodesmus Pfitzeri G. S. West, Keratococcus Dybowskii 

 n. sp., Rhabdoderma Gorskii n. sp. 9 Arten von Desmidiaceen sind 

 für den See characteristisch; unter den Flagellaten ist am häufigsten 

 Dinobryon cylindricum Imh. var. pahcstre Lemm. und daran ange- 

 heftet Stassicella dinobryonis Wolosz. (Peridinee). Man findet also in 

 dem See Kosmopoliten, einige Gebirgs- und nordische Arten, und 

 einige endemische. 



2. Jezioro Czarne bei ßereza Kartuska: Reiches Plankton, 

 besonders Pediastrum, Scenedesmus, Ankistrodesmus, Gloiotrichia 

 echinulata (Wasserblüte), Lagerheimia Chodati Bern (bisher aus Java 

 bekannte Diatomee). Für einige Scenedesmus- Arten ist eine spiralige 

 Krümmung der Kolonien (Sc. acuminatus), für andere Arten eine 

 wellenförmige charakteristisch. Manche Arten von Pediastrum 

 krummen ihre Fortsätze in gleicher Art wie P. Kawraiskyi gegen- 

 einander. Die sterilen heterocj^stenlosen Fäden von Aphanisomenon 

 flos-aquae sehen täuschend ähnlich der Oscillatoria Agardhii, viel- 

 leicht sind beide die gleiche Art. Der See sollte noch weiter studiert 

 werden. Matouschek (Wien). 



Hawkins. L. A., Effect of certain species of Fusarium on 

 the composition of the potato tuber. (Journ. Agric. Re- 

 search. VI. p. 183—196. 1916.) 



In this investigation the effect of Fusarium oxysporum Schlecht, 

 and F. radicicola Wollenw. on the sucrose, reducing-sugar, starch, 

 pentosan, galactan, and crude-fiber content was studied. Some ex- 

 periments were duplicated also with F. coetuleum (Lib.) Sacc. These 

 fungi are all parasites on the potato tuber. The tubers were sliced 

 longitudinally into four parts; the four samples, two inoculated and 

 the two corresponding control samples were placed at room tempe- 

 rature until the inoculated portions were well rotted. They were 

 then prepared and analyzed. There is considerable Variation in the 

 percentage of some of the Compounds in different quarters of the 

 same tuber; two portions of the same tuber are more nearly alike 

 in composition than samples from different potatoes. The method 

 therefore which involves the comparison of the content of two 

 quarters of the same potato is more accurate than one based on 

 comparison of the composition of two different potatoes. It has been 

 shown that the tuber-rot fungi considerably alter the composition 

 of the potato: they reduce the content of sugar, both sucrose and 

 reducing-sugar, pentosans, galactans and dry matter. The starch 

 and methyl pentosans are apparently not affected appreciably, and 

 the crude-fiber content not reduced. It was shown that these two 

 species of fungi secrete sucrase, xylanase and diastase; the last- 

 mentioned enzym is apparently incapable of acting on the ungela- 

 tinized potato starch. The experiments seem to show that enzymic 

 studies are of doubtful value in determining the effect of the para- 

 site on the host plant unless corroborated in a studj r of the physio- 

 logical relations existing between the two organisms. 



Van der Lek (Wageningen). 



Clinton, G. P., Chlorosis ofplants with special reference 

 to calico of tobacco. (Connecticut Agr. Exp. Stat. New Haven. 

 Report, p. 357—424. 8 pl. 1915.) 



Die „Calikokrankheit des Tabaks" ist nach Verf. eine infektiöse 



