i66 RESEARCHES ON FUNGI 



That the spores contained in sporangia attached to grasses, etc., do 

 actually retain their vitahty for at least nine months may be inferred 

 from the fact that at Winnipeg, in March and April, i.e. toward the 

 end of the long winter, horses fed in stables on hay which has been 

 gathered in the previous summer yield dung-balls which often produce 

 fruit-bodies of Pilobolus Kleinii and P. longiiies in great abundance. 



The sporangial wall becomes impregnated with its black pigment 

 long before the sporangium is shot away ; and, therefore, if there 

 were no subsporangial swelling, the sporangium of an intact fruit- 

 body would, when the fruit-body was turning toward the light, cut 

 off light from the stipe and render an accurate heliotropic reaction 

 to the strongest incident rays impossible. The intercalation of the 

 subsporangial swelling, which acts as an ocellus, between the black 

 sporangium and the stipe is an admirable arrangement which 

 neutralises the shadowing effect of the sporangium, enables the 

 stipe to turn the subsporangial swelling and sporangium toward the 

 source of strongest light with a considerable amount of precision 

 and, therefore, increases the chance of the sporangium being shot to 

 a distance on to herbage. 



substances are as black as those of Ccprinus, Panaeolus, etc., although they are 

 not of necessity exposed to sunlight for long periods of time. Their black walls 

 must act as a light-screen to the protoplasm contained in their interior, but it is 

 possible that the pigment is a mere by-product of the metabolism concerned with 

 the development of the wall and, for tlie spores in question, is of little or no ecological 

 significance. The black pigment in the walls of the outer cells of the shoe-string-like 

 rhizomorpha subterranea of Armillaria mellea and of the cells making up the blocking 

 layer of the mycelium of Pohjporus squamosals, Fomes applanatus, Armillaria mellea. 

 and many other wood-destroying fungi (vide /w/ra. Vol. VII),so far as the absorption 

 of light is concerned, can be of no possible ecological significance since the pigment 

 is present in structures which normally are developed only in the dark. 



In support of the view that the black pigment of the sporangium-wall of Pilobolus 

 and the black pigment of the spore-walls of Coprinus, etc., do actually protect the 

 spores from injurious radiation may be cited the recent work of Rabinovitz-Sereni 

 (" II grado di resistenza di alcuni funghi aU'azione dei raggi ultravioletti," Boll. 

 R. Staz. Pat. Veg., N.S., XII, 1932, pp. 115-144; cited from Rcrieic of Applied 

 Mycology, XI, 1932, pp. 737-738) who found that " dark thick-walled conidia such 

 as those of Helminthosporium gibberosporum, Coniosporium bambusac, and Epicoccum 

 purpurascens resisted the exposure to ultraviolet light for 180 minutes ; slightly 

 olivaceous conidia, such as those of Microascus stysanus and Pe)iieiUium crustaeeutn 

 withstood exposure for 25 minutes, while hyaline conidia, such as those of Clouo- 

 slachysaravcaria, Fusariv7)i Diartii, und the pycnospores of Deuterophonia tracheiphila 

 withstood exposure for only 10 minutes." 



