96 RESEARCHES ON FUNGI 



A few days after the spores of Coprinus sterquilinus have been 

 sown upon steriUsed horse dung in a dish-culture, hke that shown 

 in Fig. 55, the mycehum can be seen spreading rapidly over the 

 substratum in a radial direction from the points of germination. 

 Its radial rate of growth at a temperature of about 25° C. in one 

 culture was observed to be 4 cm. in 5 days or, upon the average, 

 0-8 cm. per day. Whilst this rapid surface-growth is taking place, 

 the mycelium is also penetrating into the interior of the dung- 

 balls and, about two weeks after the spores have germinated, 

 hyphae are to be found in every part of each ball. The rate of 

 penetration of the mycelium directly through a dung-ball is much 

 slower than the rate of growth upon the ball's exterior, a fact which 

 finds its ready explanation in the difference between the obstacles 

 to be overcome — in the one case hard interlacing straws, etc... 

 and in the other the air or a film of liquid. 



A mycelium produced from spores which have germinated on 

 the top of a dung-ball can grow down the sides of the ball and 

 arrive at the bottom of the culture-dish long before any hyphae 

 have succeeded in penetrating directly through the ball from top to 

 bottom. There is no doubt that the hyphae which are produced at 

 the surface of a dung-ball, some of which are in actual contact with 

 its substance and others of which project aerially to a distance of 

 a few mm., are of no small importance in faciUtating the attack 

 of the mycehum as a whole upon its substratum. Granted that 

 only part of a dung-ball under natural conditions has been originally 

 infected with the mycehum, then, by means of surface growth, 

 new radial Unes of infection may soon be brought into existence. 

 Granted that one ball only of several in a dung-mass has been 

 infected in the first place, then, by surface growth, the hyphae may 

 soon reach the other balls. In both instances the substratum 

 would be occupied much more slowly were its infection confined 

 to the penetrating hyphae and were surface hyphae absent. Owing 

 to the severe competition for the substratum which takes place 

 between coprophilous fungi under natural conditions, slowness of 

 extension of the mycehum— other things being equal— is a fatal 

 handicap, and therefore the development of rapidly-growing surface 

 hyphae which hasten the occupation of new territory is highly 



