1921] BLAKESLEE, WELCH, & CARTLEDGE—MUCORS I7z 
of transmitting spores to the cultures examined, but when the 
dishes were treated with alcohol in the manner indicated, it has not 
proved asourceoferror. Fig. 2 shows the arrangement of apparatus 
in an examination of cultures. At the left are two trays with stacks 
of cultures ready for examination. Next toward the right is a 
glass plate containing the humidor and the inverted members of 
a stack already examined. On the stage of the binocular is a 
culture under examination. The fifth dish of the stack not yet 
examined is covered by the humidor. At the extreme right is a 
series of inverted stacks which have already been examined. The 
Fic. 2.—Culture dishes and apparatus used 
stender dish marked ‘‘alcohol” contains a wad of cotton for swab- 
bing the dishes. Blotters are seen on the stage of the binocular as 
well as the paper collar which partially incloses the culture under 
examination. 
In earlier work on “imperfect hybridization”’ the bits of mycelium 
at the line of contact between two races were removed with needles 
and teased out for examination under the compound microscope 
in order to determine the presence or absence of sexual reactions. 
Unless stages in conjugation are relatively abundant, they are much 
more likely to be missed by this method than when examined at 
the proper time in the living condition under the binocular. The 
time of examination, however, must be well chosen, since if an 
examination is attempted after the line of contact between the two 
