26 4 Brown . — On the Germination and Growth of 
the total length by the total number of spores counted. This quantity 
gives a better representation of the picture presented than does a mere 
count of the percentage of germinated spores. 
Table II. 
Botrytis cinerea. 
Average Length of Germ- tube after 20 Hours Germination. 
Spore . 
Density . 
\ 
Nutrient . 
Air . 
io%C 0 2 . 
20 % C 0 2 . 
3 ° % CO; 
(h 2 o 
o*6 
0.04 
0 
0 
m/100 
T.E./ 10,000 
T.E./1.000 
i -45 
4-0 
1-0 
2.5 
0 
O-I 
0 
0 
iT.E./ioo 
6-8 
3*3 
0.25 
0 
| 
( h 2 o 
0 
0 
0 
0 
m/10 
| T.E./io,ooo 
T.E./i,ooo 
0.05 
1. 16 
0 
°-45 
0 
001 
0 
0 
.1 
( T.E./100 
5.0 
2.6 
0.25 
0 
f h 2 o 
0 
0 
0 
0 
T.E./io,ooo 
0 
0 
0 
0 
m 
T.E./i,ooo 
0 
0 
0 
0 
T.E./100 
0.52 
°-5 
0 
0 
, T.E./10 
3*35 
2.50 
0.15 
0 
We see from the above tables that, within the limits of nutrient, 
density of spore suspension, and concentration of carbon dioxide employed, 
the following factors act in retardation of germination : (1) dilution of 
nutrient, (2) increase in density of spore suspension, (3) increased concen- 
tration of carbon dioxide. The effect of these various factors is more strongly 
shown in Table II than in Table I. Thus, to take a particular instance: 
With m/100 spore suspension and in T.E./100 nutrient, the effect of 
20 per cent. C 0 2 as compared with air is to reduce the percentage of 
germination from about 100 to 25, i. e. to one-fourth; whereas the 
corresponding effect on the average germ-tube length is from 6*8 to 0*25, 
i. e. to one-twentyseventh. This is, of course, due to the fact that the 
smaller percentage of spores which have germinated in 20 per cent. C 0 2 
have on the average much shorter germ-tubes than have the corresponding 
ones in air. 
On comparing the suspensions of spores in water with those in the 
various turnip extracts, it is seen that the relative retarding effect of a given 
concentration of carbon dioxide is greater in the former case. The 
magnitude of this differential effect depends on the time at which the 
measurements are made and tends to become less as time goes on. 
Nevertheless, that the effect persists even after long time will be seen later, 
when it is shown that inhibition of germination of Botrytis spores is 
produced by 30 per cent. C 0 2 when the spores are sown in water, whereas 
a concentration of somewhat over 50 per cent, is required to stop germination 
of the spores when they are sown in nutrient. 
The retarding effect of density of spore suspension on germination is 
theoretically interesting, though in regard to infection by the spores it is 
