Feb. 1,1925 
Urediniospores of Cronartium Ribicola 
285 
Distilled water...42 cc. 
Pure glycerine.50 cc. 
Gelatine. 7 gms. 
Phenol—.....l cc. 
(Use 1 cc. fresh acid or 1 gm. of crystals.) 
Erythrosin.1 gm. in 9 cc. distilled water 
The formula is based on one given by 
Moreau. * 6 The erythrosin should be dis¬ 
solved as far as possible in the 9 cc. of dis¬ 
tilled water and the solution then added 
then measured to the nearest milli¬ 
meter with a standard white-faced 
millimeter scale. Wall thickness was 
measured to the nearest half millimeter. 
The mount was moved across the field 
of vision systematically by means of a 
mechanical stage. 
In the Field series 20 spores were 
measured from each specimen and the 
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Fig. 3—Graphs showing the ratio for the mean length divided by the mean width for 30 sets of urediniospores 
of Cronartium ribicola and Cronartium occidentale. Series and set numbers as in Figure 1 
to the glycerine gelatine mixture after it 
has been cooked but before it has cooled. 
MEASURING 
All the spores were measured by pro¬ 
jection. The apparatus 7 was so ar¬ 
ranged that the images of the spores 
were projected at a magnification of 
1,000 diameters on a white field. The 
images of such spores as fell within a 
4-inch circle in this white field were 
measurements from each 5 specimens 
grouped at random into sets, as shown 
in Table I and Table II;. but in the 
Block Island series and the greenhouse 
series 100 spores were measured from 
each specimen. Wall measurements 
were made on 50 of each 100 spores 
measured. For each series, therefore, 
there were 1,000 length measurements, 
1,000 width measurements, and 500 
wall measurements. 
Fig. 4—Graphic representation of the application of the criteria of size and shape of urediniospores to the 
biometric diagnosis of Cronartium ribicola and Cronartium occidentale. Each plotted point represents 
the length and width mean of 100 measurements. The data are taken from the figures given in Tables 
I—III for sets 1-20. Further explanation in the text 
• Moreau, F. notions de technique microscopique.—application a l’£tude des champignons. 
Bui. Trimest. Soc. Mycol. France 34; 137-191, illus. 1918. 
7 Colley, R. H. a laboratory projection apparatus. Phytopathology 14: 424-426, illus. 1924. 
