ROSE CANKER AND ITS CONTROL. 



35 



and cultural characters are certainly marked enough to be considered 

 specific rather than varietal. Since no species of Cylindrocladium other 

 than C. scoparium has been described, a new name, Cylhidrocladium 

 parnnn, is proposed for this small form. 



The morphological differences and the cultural characters and differ- 

 ences of the two species are given in parallel columns below. 



Morphological Characters. 



Since some morphological characters vary somewhat with the condi- 

 tions under which they are grown, all measurements given below were 

 taken from potato agar plates grown sinmltaneously under the same 

 conditions, and each is the average of fifty measurements. 



C. scoparium. 

 Size of spores, 48.8 x 5.1 f^. 

 Height of conidiophore, 291 fi. 

 Diameter of conidiophore stalk, 6.6 /^. 



C. parvum. 

 Size of spores, 16.8 x 2.5 /u. 

 Height of conidiophore, 130 fi. 

 Diameter of conidiophore stalk, 4.25 /^. 



Cultural Characters. 



Most soil fungi can easily be grown on a great variety of artificial 

 media. The characters of the colony differ markedly with the medium 

 used, and very frequently species of fungi, like bacteria, can be distin- 

 guished more easily by macroscopic cultural characters than by micro- 

 scopic morphological characters. Obviously, to grow each fungus on 

 all the possible media, or even a great number of them, would be almost 

 an endless task. Five common media, all easy of preparation, have there- 

 fore been adopted by the writer as standard for all diagnostic work. 

 These five are (1) potato agar (ace. Thom. Bui. 82 U. S. D. A., Bureau 

 of An. Industry); (2) sugar potato agar (the same as the potato agar 

 except for addition of 3 per cent, of cane sugar); (3) gelatin (150 grams 

 gold label to a liter of water); (4) sugar gelatin (same as above with 

 addition of 3 per cent, of cane sugar) ; (5) Czapek's synthetic agar (ace. 

 Waksman in Soil Sc. 2: 113). Petri dishes, each with a single colony 

 started at the center, were used. They were kept in the diffused light of 

 the laboratory at the ordinary laboratory temperature. 



Every reference to a color in the description below refers to the color 

 given under that name in Ridgway's "Color Standards and Nomencla- 

 ture," 1912. Color "in reverse" in these descriptions refers to the color 

 of the colony when examined from the bottom of the dish. This color 

 may be due to (1) a pigment in the medium itself (extra-cellular), (2) 

 intracellular pigments {i.e., the natural color of the mycelium), or (3) 

 very frequently it is due to a combination of the two. Sometimes a dis- 

 tinction is made between them, but for diagnostic work such a distinction 

 usually adds difficulty instead of simplifying determination. Most 

 emphasis is placed on those characters which appear within the first 



