156 RESEARCHES ON FUNGI 



where x represents the fractional loss of volume in the heavy fluid, 

 v the volume of the spore in water, s the apparent specific gravity 

 of the spore in the heavy fluid, s' the true specific gravity of the 

 spore in water, and s" the specific gravity of water itself. 



Since = |, s=l*43, and s"=l, we find that s'=l'215, or the 

 true specific gravity of the Coprinus spores in water is approxi- 

 mately 1-21. 



In the case of the Mushroom, owing to the spores becoming 

 indented on one side, the exact loss of volume of the spores in a 

 calcium chloride solution of sp. gr. 1-31 could not be measured 

 directly. However, it was estimated by inspection as being from 

 about one-third to one-half of the volume in water. On this 

 assumption we may calculate from the equation already given that 

 the specific gravity of Mushroom spores is approximately 1*2. 



' The Amanitopsis spores did not show any appreciable con- 

 traction in the calcium chloride solution or cane-sugar solution 

 of sp. gr. 1 - 02. Since we have already found that the real specific 

 gravity of the spores in water must lie between 1 and 1*02, we 

 may take it that the real specific gravity is approximately 1*02. 

 This approximation must certainly be correct to within 1 per 

 cent, of the actual specific gravity. 



Another method for estimating the specific gravity of spores 

 is that of measuring the rates of fall of the spores in air and in 

 water. The data so obtained are then used in the following 

 equation, which can be deduced from Stokes' Law which must be 

 assumed to be true : 



v'^p-I^n 

 v p M' 



where v' is the velocity of the fall of spores in water, v the velocity 

 of fall in air, p, the viscosity of air, p the viscosity of water, and p 

 the specific gravity of spores. 



A counting apparatus, with a chamber 1 cm. square above and 

 below and 0*2 mm. deep, was used for estimating the rate of fall 

 of the spores in water. The chamber was filled with water holding 

 spores in suspension and covered with a cover-glass. A microscope 

 was then turned into the horizontal position and the counting 

 apparatus clamped down to the now vertically-placed stage. The 



