The Lycopodium Method of Qioantitative Microscopy. 175 



The counts of spores in twenty fields were, 22, 25, 19, 18, 32^ 

 4, 13, 10, 20, 25, 24, 26, 9, 18, 7, 10, 10, 22, 29, 30, giving a total 

 of 373 spores. 



Area of 20 fields . . . . = 20 x 0*2003 sq. mm. 



= 4 '006 sq. mm. 

 Area of the cover-glass . . . = 322 sq. mm. 



Nmnber of spores under the cover-glass 



373 X 322 



4-006 

 29,983 



Nmnber of spores per milligramme . = ^9, 983 x 9-856 

 ^ 0-0276 X 110-2 



= 97,170 



The mean of twenty-six determinations was 93,000. This 

 figure was confirmed by calculation from the linear dimensions and 

 the specific gravity of lycopodium spores, which gave the number 

 95,000. The mean of the results is therefore 94,000 (IS). 



Determination of the Number of Starch Grains 

 PER Milligramme of Maize Starch. 



The number of starch grains per milligramme of starch dry at 

 100° C. can be used to characterize a starch. The figure was found 

 by the following method in the case of a sample of commercial 

 maize starch: — 0*2 grm. of lycopodium was mixed with 0*1 grm. 

 of maize starch and about 20 c.c. of olive oil. Four slides were 

 prepared by mounting drops of the suspension, and the counts 

 obtained gave 480, 477, 436, and 410 starch grains respectively, or 

 on an average 450 grains for every 100 lycopodium spores. Hence 

 there are 450 X 94,000 -^ 100 starch grains for every milligramme 

 of lycopodium, and since this weight of lycopodium was mixed 

 with 0-5 milligramme of starch there are 2 x 450 X 94,000 -r- 100 

 = 846,000 starch grains per milligramme of air-dry starch. Allow- 

 ing for 13*4 p.c. of moisture, there are 846,000 x 100 -^ 86 "6 

 = 977,000 grains per milligramme of maize starch dry at 100° C. 

 This number represents the sample of maize starch examined, but 

 further research is needed before one can regard it as characteristic 

 of maize starch in general. 



Other Practical Applications. 



Examples of the use of these figures as a means of standardiza- 

 tion are to be found in the determination of the number of pollen 

 grains present in such powders as Kousso and Insect Flowers. 

 Kousso is a well-known anthelmintic, and consists of the dried 



