226 RESEARCHES ON FUNGI 



clamp, and then looks along the spore-bearing glass surface with 

 the low power of the microscope, one sees that each spore appears 

 to be flat or even slightly concave above and convex below, the 

 hilum always being on the upper side of the spore and directed 

 upwards (Fig, 95, F, L). A combination of the views described 

 under (1) and (2) proves that each one of the dried spores has a boat- 

 shaped form, its concave depression being directed upwards and 

 its rounded keel downwards. 



Hitherto, we have considered the case of a spore which has 

 settled before it has undergone any contraction due to loss of 

 water. However, in nature, owing to the air not being fully 

 saturated with water vapour, it must usually happen that a liberated 

 spore, immediately after being set free and long before coming to 

 earth, undergoes partial or even almost complete desiccation. No 

 doubt such a spore, whilst still being carried about by the wind, 

 takes on a boat-shaped form (Fig. 95, G, H, I, J) exactly like that 

 already described. A boat-shaped spore, suspended in the air, 

 always falls with its hollow upwards and its rounded keel down- 

 wards (I, J), for in that position alone the whole spore is in a position 

 of stable equilibrium. Experimental evidence supporting these 

 assertions was obtained in the following manner. A box, six feet 

 high and about half a square foot in transverse section, was set up 

 in a room ^ which contained very dry air. To the top of the box, 

 within, was pinned a pileus of Coprinus sterquilinus which was 

 discharging spores and, on the bottom, was laid a glass slide. Then 

 the box was closed, whereupon spores began to accumulate on the 

 slide, so that a thin spore-deposit was soon formed. When the 

 slide was examined under the microscope, it was found that the 

 spore-deposit had exactly the same appearance as a spore-deposit 

 (c/. Fig. 94) collected in damp air close beneath a pileus covered 

 by a bell-jar, i.e. all the spores in it were boat-shaped and had their 

 hollows directed upwards and their rounded keels downwards. 

 Now, since, owing to their slow rate of fall in still air,^ the spores 

 must have taken upwards of five minutes to fall the six feet between 

 the pileus and the slide upon which they came to rest, and since 



1 A warm laboratory, heated by steam radiators, in mid-winter, at Winnipeg. 



2 Cf. p. 220. 



