THE SPHAEROBOLUS GUN 367 



those spores which do not settle on herbage are almost certain to 

 perish without ever producing a mycelium. 



The fungi of Group II have dispensed with the wind as an agent 

 in the dispersal of their spores. Instead of shooting away their 

 spores singly to a short distance and entrusting them to the uncer- 

 tain operation of the wind which would deposit them indiscrimi- 

 nately in places favourable or unfavourable so far as their ultimate 

 fate is concerned, they shoot them away in the form of large spore- 

 masses and very violently, so that they at once strike and stick to. 

 or fall upon, the surrounding vegetation. The spore-masses are 

 so heavy that, despite the wind, their trajectory is a parabolic one 

 and they come to earth within about one second after being 

 discharged. Hence the spore-masses must settle on herbage within 

 a few feet of the fruit-bodies which have discharged them. For the 

 ultimate fate of the spores such a place of settlement is highly 

 favourable ; for herbivorous animals must have been there before 

 and are therefore likely to come again and, when they come, they are 

 likely to swallow the spore- masses with grass, etc., as they feed. 



Thus, in the fungi of Group II, the deposition of the spores 

 on herbage is secured directly through the activity of the fruit- 

 bodies, and not indirectly by the wind as in the fungi of Group I, 

 with the result that the chances of a high percentage of the spores 

 being swallowed by herbivorous animals and finding their way into 

 dung are greatly increased. A comparison of the arrangements for 

 depositing spores on herbage exhibited by the two groups of copro- 

 philous fungi leads to the conclusion that the fungi of Group II are 

 far more highly specialised and more closely adapted for a copro- 

 philous mode of existence than are those of Group I. 



Sphaerobolus as a Lignicolous Fungus and the Problem of its 

 Mode of Infecting Wood. — As already pointed out, Sphaerobolus 

 very frequently occurs on wood. It may therefore be asked : if 

 Sphaerobolus is primarily a coprophilous fungus, how does it enter 

 sticks, stumps, and pieces of worked wood on which it is so often 

 found ? Since under natural conditions no one has yet observed 

 the exact means by which a specific piece of wood has become in- 

 fected with Sphaerobolus, for the present we are obliged to answer 

 our question in a tentative and somewhat speculative manner. 



