Lutman—Life History and Cytology of the Smuts. 1201 
distinguished by the smear from the agar culture as described 
below. It required 5-10 days for the colonies to attain suf¬ 
ficient size for use when they were kept at these low tempera¬ 
tures. 
In the meantime the oat seedlings were being grown in moist 
filter paper. Seedlings about 2-3 days old and whose leaf 
sheathe was not longer than 1 cm. were used for inoculation, 
those with leaf sheathe about 1/2 cm. long being preferred. 
The conidia from the colonies on the plates were now spread on 
the young leaf sheathes with a scalpel. The infected seedlings 
were then replaced in the damp filter paper and put back in the 
refrigerator at a temperature of about 12° C. After being kept 
there for 5-7 days they were planted out in soil in large pots. 
By peeling off the epidermis under the infected area and ex¬ 
amining it with the microscope the process of infection could be 
readily followed. The first penetration of the epidermis oc¬ 
curred after 2-3 days and after 5 days many of the epidermal 
cells were full of the smut mycelium. Keeping the seedlings at 
a low temperature greatly retards their growth without seeming 
to have nearly so great an effect on the fungus growth, thus giv¬ 
ing the latter as nearly as possible the conditions that are said 
to favor its growth in nature and cause such high percentages of 
smutted heads, i. e., cold, damp spring weather. The infection 
of the growing point of the young plant cannot be seen from the 
outside but in sections it was found to be infected after about 10 
days. 
While this method of securing infected heads has been found 
very successful, the percentage of infection obtained is also de¬ 
pendent on the season when the inoculation is made and the rate 
of growth of the oat plants. Plants infected in this way about 
Sept. 1st and kept in the green house over winter did not come 
to maturity until about Peb. 1st when they showed about 95% 
of infected heads. Another lot infected April 1st, came to ma¬ 
turity about June 1st and only showed about 50% of infected 
heads. I am inclined to believe that this difference was not due 
to increased immunity from infection but to a higher percentage 
of recovery after infection. The winter conditions in the green 
5—S. & A. 
