i6o Journal of Agricultural Research voi. x. no. 4 



dies along with the seed. This is indicated by the macroscopical and histo- 

 logical appearance of the seed, and also by the results of the germination 

 tests, in so far as the negative results can be held to justify a conclusion. 

 It might readily be expected to happen in seed so small as those of the 



turnip. 



IDENTITY OF THE FUNGUS 



The form genera Colletotrichum and Gloesporium, comprising the 

 group to which this organism belongs, are very difficult to separate 

 into species because of the fact that many species are morphologically 

 very variable and are rather general parasites — that is, a single species 

 may infect and produce some form of disease in a great variety of host 

 plants, as shown by the work of Shear and Wood ^ and others. There- 

 fore one is necessarily more or less uncertain as to just how much reliance 

 should be placed on morphological structures or on inoculation tests 

 in determining the limits of species. 



The results of cross-inoculations indicate that the turnip fungus is 

 probably not identical with either Glomerella lindemuthianum, G. gossypii, 

 or G. cingulata. The last-named species, however, according to the views 

 of Shear and Wood,^ contains several forms which are more or less dis- 

 tinct both morphologically and phisiologically. Therefore, if this view 

 is accepted, it is impossible to determine the limits of this species in the 

 absence of the ascigerous stage. 



Two related forms, Gloeosporium concentricum (Grev.) Berk, and Br.^ 

 and Colletotrichum brassicae Schulz and Sacc.,* have been described on 

 species of Brassica. Unfortunately specimens of neither of these could 

 be obtained for comparison; but specimens of the turnip fungus were 

 sent to Dr. C. L. Shear, of the Bureau of Plant Industry, who compared 

 it with G. .concentricum, which, he says, is entirely distinct. He expressed 

 the opinion, however, that the turnip fungus might be identical with 

 C. brassicae, specimens of which were not available to him. " This species 

 was described as occurring on decaying stems of Brassica oleracea and 

 B. caulocarpa; but the characterization was very brief and, in view of 

 the recent work in this group, is of little value in determining relation- 

 ships. 



The fungus and the disease produced on turnip leaves is characterized 

 as follows: Spots small, circular, or nearly so, 2 to 5 mm. in diameter, 

 sometimes anastomosing and forming larger spots of irregular shape, 

 pale grayish or straw colored; acervuli small, scattered over both lower 

 and upper surface of spot; stromata subepidermal, delicate; conidiophore 

 short, tapering abruptly to a slender sterigmata to which the spore is 

 attached; conidia cylindrical, 13.5 to 19.5 by 4 to 5.5 fi, hyalin, i-celled; 

 setae dark brown to black, slender, 20 to 42 by 3 to 5 ix, i- to 3-septate. 



• Shear. C. L., and Wood, Anna K. Op. cit. 



^GrevillE. R. K. SCOTTISH CRYPTOGAMic FLORA. V. I. pi. 27 (col.). Edinburgh, 1823. 

 SSCHULZER VON MuGGENBURG, Stephan, and Saccardo, P. A. micromycetes sclavonici novi. 

 In Rev. Mycol.. anu. 6, no. 22, p. 79. 1884. 



