96 KESEARCHES ON FUNGI 



upon a suitable Avoodco stand, so that the front lens Avas about 5 

 feet above the ground. To the lens was attached a black cap, in the 

 middle of which a round aperture, one and a half inches in diameter, 

 had been made. A bull's-eye condenser — a plano-convex lens 

 mounted upon a stand adjustable for any position, such as is com- 

 monly used for illuminating opaque objects — was then placed in 

 front of, and close against, the aperture so that, when the arc was 

 turned on, the condenser formed a concentrated beam of light. The 

 chamber into which the spores were liberated usually consisted of 

 a beaker, G inches high and 4 in diameter, closed above by a 

 circular glass plate (Fig. 37). A piece of sheet cork was fixed on to 

 the middle of one side of the plate by means of sealing-wax. A 

 living fruit-body, to be tested, was pinned on to the cork so that, 

 when the plate was placed on the beaker, the fruit-body had its normal 

 orientation, the hymenial side looking downwards. The beaker Avas 

 then set close in front of the condenser in the beam of light. 



If a fruit-body is active, a stream of spores can be detected 

 coming from it within a few seconds after it has been placed in 

 position above the beam. The stream is carried slowly round and 

 round in the beaker by convection currents. It gradually breaks up 

 so that in a few minutes the spores are well scattered (Fig. 37). A 

 maximum density of spores is soon attained. At this stage as many 

 spores settle as are liberated. If one directs the beam of light so 

 that it passes through the air just beneath the gills or hymenial 

 tubes, &c., one can observe the spores slowly emerging into vicAV. 

 They are then simply falling by their oAvn weight, at the rate, in 

 many species, of 1-2 mm. per second.^ Convection currents sweep 

 the spores, as they emerge from the gills, hymenial tubes, &c., slowly 

 in one direction, and it is thus that a steady stream of spores arises. 

 The density of the stream remains very regular for hours or even 

 days. There is no evidence Avhatever that the spores are discharged 

 intermittently. The most remarkable thing about the liberation of 

 the spores is just its constancy for considerable periods of time. An 

 unbroken stream of spores was observed to be emitted from the fruit- 

 bodies of species of Polystictus, Lenzites, Schizophyllum, Stereum, 

 &c., for days and in some cases for more than two Aveeks. 



^ Vide infra, Chaps. XV. iui<l XVT. 



