74 RESEARCHES ON FUNGI 



sterilised horse dung contained in large crystallising dishes covered 

 with glass plates ; and the dishes were kept in the light on a 

 laboratory table. The mycelium of these polysporous cultures, 

 undoubtedly, must have been secondary (diploid) in character, 

 owing to the union of primary mycelia of opposite sex. Yet among 

 the numerous, grey, perfectly fertile fruit-bodies produced in the 

 course of two or three weeks a few equally large, yellowish-white, 

 sterile fruit-bodies always made their appearance. Here, there- 

 fore, the sterility cannot be associated with the haploid condition 

 of the mycelium, but must be due to some other factor. Perhaps 

 this other factor is too great a luxuriance in the production of fruit- 

 bodies. On unsterilised horse dung, under natural conditions, the 

 fruit-bodies of Coprinus lagopus are usually not so crowded or so 

 large as in the artificial cultures just described, and usually they are 

 all fertile. In the artificial cultures the lack of competition with 

 other organisms results in the coming to maturity of a larger number 

 of rudimentary fruit-bodies than normally occurs in nature. 

 Thereby the balance between the capacity of the mycelium for 

 supplying growth materials to the fruit-bodies on the one hand 

 and the size and number of the fruit-bodies actually produced 

 on the other hand may be upset, so that some of the fruit-bodies 

 do not obtain the quantity of growth materials requisite for their 

 full development and suffer partial starvation when just about to 

 expand. Possibly, therefore, the imperfect development of the 

 hymenium in some of the fruit-bodies is simply due to lack of 

 vigour brought about by imperfect food supply from the mycelium. 

 An analogy, perhaps, is to be found in Apple trees which often set 

 many more fruits than they can possibly bring to perfection. When 

 this happens, as is well known, many of the apples cease their 

 development when about one-quarter grown and, whilst still green 

 and sour, fall to the ground. The half-developed fruit-bodies in 

 the sterile cultures of Coprinus lagopus perhaps compete for the 

 materials necessary for their development held within the mycelium 

 much in the same way that the partially developed apples upon an 

 Apple tree compete for the materials necessary for their develop- 

 ment held within the twigs, with the result that some are beaten in 

 the struggle and only undergo imperfect development. 



