262 
Brown. — On the Germination and Growth of 
is readily determined to within o-i per cent. With care, much greater 
accuracy is possible, but this was rarely required. From numerous analyses 
it was found that with ordinary care the carbon dioxide content of the 
experimental atmospheres as set up in the manner above described never 
varied by more than \ per cent, from the value intended. 
Determinations of the oxygen content were only made occasionally, 
and were carried out by means of the same apparatus. 
The following is a list of the fungi used at one time or other in the 
course of the present investigation, together with a statement of the source 
Originally obtained from Centralbureau 
voor Schimmelcultures, Holland. 
Isolated from onion. 
All stock laboratory cultures. 
All isolated from rotted apples. 
and a Botrytis cinerea , also obtained from apple, and which appeared to be 
identical with the other culture of this organism. 
Stock cultures of these fungi were grown at laboratory temperature in 
diffuse light on sloped tubes of potato agar. 
from which they were derived : 
Botrytis cinera 
B. parasitica. 
Aspergillus repens \ 
Mucor sp. 
Rhizopus nigricans f 
Penicillium glaucum ) 
Monilia cinerea \ 
Fusarium sp. 
Phoma roseola }- 
Alter naria grossulariae 1 1 
Sphaeropsis malorum 
Experiments dealing with the effect on Germination of various concentra- 
tions of Carbon Dioxide and Oxygen. 
The general nature of the effects produced was worked out in the first 
instance with spores of Botrytis cinerea. A series of experiments was 
carried out showing the relation between the amount of germination and 
the following three factors : (1) concentration of carbon dioxide in the 
atmosphere ; (2) density of spore suspension ; (3) concentration of 
nutrient. 
The effect on germination (determined quantitatively as percentage of 
spores germinating or as the average length of the germ-tube produced) 
of the second and third of the factors mentioned was known from earlier 
work to be as follows. The amount of germination in a given time increases 
with concentration of the nutrient up to a certain limit. 2 The amount of 
germination in a given nutrient decreases with increasing density of spore 
1 Identified as such by Horne. Ann. Appl. Biol., vii. 190, foot-note 3, 1920. 
2 Cf. Brown, this volume, p. 108. 
