New York Agricultural Experiment Station. 193 



Plate XXV, Fig. 1.) Specimens of this peach knot were sub- 

 mitted to Mr. A. D. Selby, botanist Df the Ohio Experiment Sta- 

 ton, who identified them as being the same as the " twig disease 

 with gum flow" discussed by him in Ohio Experiment Station 

 Bulletin 92, pages 199-206. The knots are almost invariably 

 covered with gum. In midwinter we examined many of these 

 knots collected in different localities and nearly always found 

 spores of HelmintJiospoi^um (apparently H. ca/rpopMlum) in the 

 gum. Sometimes the spores were abundant. 



Hyphae are not abundant in the tissues of the knots. In fact, 

 it is not clear that they contain any hyphae except occasionally 

 those of saprophytes. 



A pure culture of the HelminihospoHum on the knots was ob- 

 tained and peach twigs inoculated with it. The inoculated 

 twigs became much blackened at the point of inoculation and 

 there was a copious exudation of gum, while on the check twigs 

 there was no blackening and very little gum. Although the fun- 

 gus seemed to be parasitic the twigs manifested no tendency to 

 form knots. 



In the latter part of the season we occasionally found peach 

 twigs which were killed by the same Helminthospot'ium. In such 

 cases the twig was strangled at a point from 6 to 12 inches back 

 of the tip. At the point of attack the bark was of a gray color 

 and Helminilwsponum spores were plentiful, but there was no 

 enlargement of the twig. 



We have also sought for HelmintJiosporium on peach leaves, 

 but without success except in one instance. In the Station 

 orchard some peach trees, the fruit of which was infested by 

 Eelminiliosporium, showed considerable shot-hole injury on the 

 leaves. An examination of the affected leaves was made Sep- 

 tember 4. Most of the spots had fallen out, but on those re- 

 maining we occasionally found Eelmintliosporium spores iden- 



ium the germination is often of a peculiar sort. (See Plate XX, Fig. 7.) 

 The average dimensions of 17 spores grown on sugar beet agar was 

 131/^x35 ju. As found in nature on the fruit and branches they are som©- 

 wbat smaller. 



13 



