33 
Tbe colorless conidia are usually spherical; they are all spherical when 
first born, but some of them become somewhat irregular or oval from the 
pressure of contiguous conidia in the large heads. They measure 1$ to 2+ 
microns, sometimes reaching 3 microns when oval. 

Fig. 16.—Isaria tomicii. a, germinating spores; b, the same two days later; c, anas- 
tomosing threads after four days; d, eé, formation of clusters of conidia, after one week: 
jf and g, mature clusters of conidia after twelvedays, Original. 
On potato the growth quickly spreads over the surface in a loose, fluffy, 
white growth, which rests on the surface of the liquid and causes the 
potato to turn a beautiful purple color, very deep and intense. The 
growth soon increases until the diameter of the tube is entirely filled and 
the threads force their way upward fora distance, becoming slightly 
creamy in color. No Isaria-sporophore has as yet been observed. In 
half-litre Erlmeyer flasks, in which pieces of sterilized potato were placed, 
no sporophores were produced, and the growth was essentially the same 
as in the test-tube. 
