THE SPECIFIC GRAVITY OF SPORES 155 



in volume, if such there is, in spores of Amanitopsis vaginata in 

 a solution of sp. gr. P02 is so small as not to be observable. The 

 heavy-fluid tests only give us the apparent specific gravity of the 

 spores. There seems to be little doubt that the decrease in volume 

 is due to loss of water which passes out from the spores by osmosis 

 in accordance with well-known laws. Loss of water from the spores 

 must of necessity increase their specific gravity, for the salts and 

 other bodies heavier than water must thereby become concentrated. 

 We can conclude, therefore, that the apparent specific gravity of 

 the spores in the heavy fluid is greater than the specific gravity 

 of the spores when fully expanded in water. The tests with the 

 solutions inform us that the true specific gravity of the spores is 

 between 1 and 1*43 for Coprinus plicatilis, between 1 and 1/32 

 for Psalliota campestris, and between 1 and 1*02 for Amanitopsis 

 vaginata, In the last-named species the result obtained with 

 calcium chloride was confirmed by means of a solution of cane- 

 sugar. 



By determining the loss of volume of spores of Coprinus 

 plicatilis when placed in a calcium chloride solution of sp. gr. 143, 

 I have been able to calculate approximately the true specific gravity 

 of the spores in water. 



With the aid of a Poynting Plate Micrometer the spores were 

 measured with a considerable degree of accuracy. Ten long, ten 

 short, and ten intermediate axes were measured, each measurement 

 being made on a different spore. The average size of the spores 

 was thus found to be — 



In water 12-54 x 10-33 x 8-14 



In CaCl 2 solution, sp. gr. 1*43 . 11*76 x 10*18 x 4*5 

 By multiplying the three axes together we can calculate that on 

 the average for each spore — 

 (volume in water) : (vol. in CaCl 2 solution, sp. gr. 1-43) : : 1054 : 538. 

 We may conclude, therefore, that when a spore is taken from 

 water and placed in the calcium chloride solution, its volume is 

 approximately halved. 



Now, it may be shown that 



(1 —x)vs-\-xvs" = vs' 



