4 THOMAS: INFECTION OF APIUM GRAVEOLENS 
ments with celery in the greenhouse, where the health of the host 
was altered by various experimentally controlled conditions. 
Each set of plants was accompanied by control plants and no 
attempt has been made to compare in any detail plants inoculated 
at different dates or plants which for any reason cannot be referred 
to the same control plants. Some experiments with hosts other 
than celery were made to show the host range of the Septoria 
and will be taken up in detail later in the paper. The plants 
were grown in pots usually in garden oil which was screened and 
mixed to obtain uniformity. Inoculations were made by atomiz- 
ing with a suspension of spores taken from infected leaves. The 
plants of a series were placed in a group, alternating test and con- 
trol plants, and were atomized from above and from the sides to 
obtain maximum dosage. The spore suspension was diluted in 
one case I to 10 and in another 1 to 20 without any marked de- 
crease in the amount of infection produced. The counts in these 
cases were not high, however. The inoculation chamber was a 
rectangular box constructed from window sashes and lined with 
burlap which was saturated with water at the time of inoculation. 
The plants were usually kept in the inoculation chamber about 
forty-eight hours. Since Septoria spreads only slightly in the 
dry atmosphere of the greenhouse and since celery is little 
affected by other pests under these conditions, this is a particu- 
larly convenient form for study. The difficulty of accurately 
measuring the amount of infection was obvious here as in all 
infection experiments. However, when only plants of equal age 
and approximately equal size are compared it seems accurate to 
count the total number of spots per leaf or per plant. This 
method is not satisfactory in older plants in variety tests since 
there is considerable difference in the size of mature plants of 
different varieties. The methods employed for the computation 
of leaf area are too unwieldy for use with plants in any considerable 
numbers. 
NAME OF THE PARASITE 
The specific name of the Septoria under consideration is in- 
volved in one of the more or less hopeless name tangles which 
serve so frequently to confuse the minds of botanical workers. 
Chester (4) in making one of the earliest reports (1891) on the 
