378 BOTANICAL GAZETTE (JUNE 
7. When the stem was cut into at the surface of the ground 
and mycelium and conidia inserted, no effect was apparent. 
From these experiments it appears that the typical “ drop” 
cannot be produced from Botrytis conidia in vigorous lettuce 
plants under ordinary conditions. 
The following experiments were made with lettuce seedlings. 
A dish of soil was sterilized and then thoroughly inoculated with 
fresh Botrytis conidia. Lettuce seed wasthensown. The plants 
came up well and remained entirely unaffected. The soil was 
then sprinkled heavily with conidia among the seedlings, with 
the result that one ‘damped off.’’ The stem was permeated 
with a mycelium entirely similar in appearance to that found in 
the “drop.” A portion of this is shown in fig. 27 (cf. fig. 57). 
The dish was then covered with a bell jar and kept very 
moist, but no more plants were affected. Prune juice containing 
conidia was then poured amongst the plants and the dish kept 
in the open air. ‘‘Damping” at once set in, and in a few days 
all the plants succumbed in the characteristic manner. Cultures 
made from these plants on prune and turnip showed the parasitic 
peculiarities of Botrytis already referred to. A considerable 
mycelium was produced at first but very few conidia until later. 
Raw turnip was readily attacked and caused to rot. This expeti- 
ment corroborates Kissling’s* results in regard to Botrytis cinerea 
that conidia are unable to, or at least do not readily, attack living 
tissue except after previous saprophytic nourishment. 
In respect to the general question as to the relation of 
Botrytis to the “ drop,” these results seem to show that the disease 
is not produced in vigorous plants by direct infection from conidia 
in the air or soil, although in the case described above, where 
the vitality of the plants was very low, such appears to have 
been the case. The same conclusion may be deduced from the 
usually sucessful result of sterilizing the soil. There appears to 
be no doubt that the cases where “ black root” develops into the 
“drop” belong to this form of the disease, and also the trouble 
which Humphrey, Galloway, and Bailey had in mind in referring 
* Hedwigia 28: 227. 18809. 
