486 Brooks . — Observations on the Biology of Botrytis cinerea . 
deprived of potassium were intermediate in size between those described in 
the first category and the latter. In all cases, however, the plants appeared 
to be quite vigorous. One might suppose that after six weeks’ active 
growth the influence of the reserve materials stored up in such seeds 
as those of the Lettuce would be greatly minimized ; and that the absence 
from the soil of certain of the normal mineral constituents would be felt 
throughout the regions where metabolism was in progress. At this stage 
Botrytis spores derived from diseased Lettuces were placed directly upon 
the leaves of the different cultures, the precaution having been taken of 
cutting off any yellowing leaves present. In none of the plants, however, 
did any sign of infection ensue. The inoculations were repeated, the spores 
being placed this time in drops of water upon the leaves. There was the 
same negative result as before. The whole series of cultures was repeated 
twice, but in no case did any evidence come to hand that the deprivation of 
certain mineral substances from the soil would induce the plants grown in 
it to succumb to direct infection by the spores. 
It is clear, therefore, that, even by a great reduction in the amount 
of certain mineral constituents available, no such change can be induced in 
the constitution of the green plant as would account for the penetration of 
the germ-tubes of Botrytis. One supposes that the amount of food material 
stored up in the seed, together with the water and mineral substances 
absorbed from the soil and the carbon fixed from the air, enables the 
ordinary plant machine to elaborate a certain amount of protoplasm. If, 
e. g. a certain mineral substance is deficient in quantity, a less amount 
of protoplasm will be formed, but the protoplasm produced under these 
conditions will be of the same * quality ’ — if one can use such a term — as that 
produced under conditions of normal nutrition. And if the protoplasm of 
plants grown under conditions of mineral starvation is of the same ‘quality ’ 
as that of plants grown under normal conditions, there is no likelihood that 
the constitution of the former plants will be such as to lead to infection by 
the germ-tubes of Botrytis. 
The results here obtained may be compared with those of Marshall 
Ward in regard to the parasitism of Puccinia dispersa upon species of 
Brome grasses grown under conditions of mineral starvation. He found 
that starvation of the host had no appreciable effect upon the ability 
of this fungus to infect. Of course the method of infection of Botrytis 
cinerea is totally different from that of Puccinia dispersa , but the aim 
of the culture experiments was the same in each case. With Botrytis , 
whose conidia are unable to infect the leaves of the normal Lettuce plant, 
and with Puccinia dispersa , whose uredospores readily infect the Brome 
grass, the influence of mineral starvation of the host upon the inability 
or ability to cause infection, respectively, was nil. The work on Botrytis 
outlined here confirms Marshall Ward’s view that f whatever may be the 
