A SERIOUS LETTUCE DISEASE. 
119 
turbed half apothecia were formed normally. More than 10 were 
counted at 25 days after planting. In the half of the flat in (Fig. 23) 
which the soil was stirred, no apothecia at all were formed even after 
60 days’ test. 
1 2 
Fig. 23. —Flat showing the effect of stirring the soil upon the formation 
of apothecia. 1, Not stirred. 2, stirred every two weeks. 
The Ascophore. 
To determine the effect of mutilation of the ascophore, sclerotia 
were germinated and the stipes, as soon as they began to expand, 
were cut off at various distances from the apex. It was found that 
these stipes ceased to develop, except when they were cut just at the 
base of the forming disk. In such cases, however, new disks began 
to develop at once and sometimes two or three appeared upon the end 
of one mutilated stipe, Fig. 24. 
To ascertain the effect of light or darkness upon the formation of 
the ascophore a flat was divided into four sections and planted De¬ 
cember 14, 1906, with sclerotia. The first section was left uncovered, 
the second was covered with unprinted newspaper, the third with light 
weight manilla paper and the fourth with heavy weight manilla pa¬ 
per. Examination on February 5, 1907, showed that disks were fully 
formed upon section one, uncovered, though no disks showed in any of 
the other sections (Fig. 25). On February 27 the paper was all re¬ 
moved, and on March 11 very numerous disks were first observed on 
these newly uncovered sections. The time which elapsed between the 
removal of the paper and the appearance of the disks was consid¬ 
erably less than is usually taken to produce ascophores and it is 
