66 Eei'okt of the Botanist, of the 



THE STEM ROT. 



In December, 18^8, we observed a stem rot or perhaps it might 

 more appropriatelj be called a branch blight working among some 

 Antirrhinumfi in one of the Station greenhouses. During the 

 remainder of the winter and the following spring this disease 

 became common and caused considerable damage. The same dis- 

 ease appeared again last winter, but not so destructively. 



It attacks chiefly the succulent shoots, causing several inches 

 of the terminal portion to wilt and die. In some cases, particularly 

 on shoots which have become somewhat woody, a section of the 

 stem an inch or more in length turns brown, while the portion 

 beyond remains green. In a short time, however, the whole 

 branch dies. More frequently all of the affected portion wilts 

 and becomes discolored without the appearance of a spot at any 

 particular place on it. The point of attack may be close to the 

 soil, but is usually at considerable distance above it, and never 

 below it so far as observed. 



In all cases numerous pycnidia of a species of Plioma soon 

 make their appearance on the lower part of the affected portion. 

 In the course of the investigation other fungi were sometimes 

 found on the diseased stems, but the Phama was so abundant and 

 eo constantly present that it was suspected to be the cause of 

 the trouble. Pure cultures of the Phoma were obtained and 11 

 succulent shoots inoculated with it, as follows: About three 

 inches below the tip of each shoot a puncture was made, a small 

 quantity of fungus inserted, and then the puncture covered by 

 wrapping the stem with grafting wax. Ten check shoots were 

 treated in identically the same manner, except that no fungus was 

 inserted in the puncture. 



The inoculations were made April 30th. At the end of five 

 days four inoculated shoots were wilted; two more wilted on the 

 eighth day, two others on the ninth day, and on the eleventh day 

 all eleven inoculated shoots were fully w^ilted. Seven of them had 

 rotted so badly at the point of inoculation that they had broken 

 over and the tops hung down. As late as June 19th, seven weeks 



