170 RESEARCHES ON FUNGI 



I happened to be writing to the late Dr. Roland Thaxter of Harvard 

 University and, in the course of my letter, hoping to receive from 

 him some comment on the matter, I mentioned the new Pilobolus 

 and gave a brief description of it . In his reply he informed me that he 

 had known my P. uinhonatus for forty years and that its chief sub- 

 stratum was sheep dung.^ Thus the species occurs not only in central 

 Canada but also in the eastern part of the United States of America, 

 General Description. — Pilobolus umbonatus was obtained 

 upon horse-dung balls taken from the streets of Winnipeg in mid- 



'*^.^ 







Fig. 82. — Pliotomicrogia.pli ot a mass of spores of 

 Pilobolus umbonatus (small, ellipsoid) together with 

 five spores of P. longipes (large, rounded-oval). 

 Magnification, 510. 



winter of the years 1931-1932 and 1932-1933. The balls were 

 brought into the laboratory and were placed in a crystalhsing dish 

 covered with a glass plate. Soon they thawed and, after a few days, 

 the fruit-bodies of the new species began to appear upon them. 

 New crops of fruit-bodies came up each day for four or more days 

 in succession. Well-grown fruit-bodies are 7-9 mm. in length but 

 much shorter fruit-bodies have often been seen (c/. A and B in 

 Fig. 105, p. 210). It was observed on one dung-ball that the length 

 of the fruit-bodies diminished as successive crops appeared : on the 



1 Roland Thaxter : "I have known that ' umbonate ' Pilobolus for many 

 (40) years. You will find that on its natural substratum, which is more commonly 

 sheep dung, it varies from a sharply pointed type to one which is quite bluntly 

 rounded." In litt., Feb. 12, 1932. 



