560 
Notes. 
Examples : 
(1) Bright day — temp. ~ 20°C. Sycamore shoot. 
In window — air still. 
Time required =39 min. 
Water transpired = 50 x -00895 = 0-447 c.c. 
Area of leaf = 155 sq. cm. 
1 sq. metre of leaf transpires 44 c.c. per hour. 
(2) Bright diffuse daylight — temp. = 2i°C. 
Out of doors. 
Time required = 16 min. 
Water transpired = 0-447 c.c. 
Area of leaf = 286 sq. cm. 
1 sq. metre of leaf transpires 59 c.c. per hour. 
A. D. HALL. 
South Eastern Agricultural College, Wye. 
THE BROMES AND THEIR RUST-FUNGUS (Puccinia 
dispersa).— I have for some time been occupied with an investigation 
which has involved a comparative examination of the ‘seeds’ and 
seedlings of all the species and varieties of the genus Bromus that 
I could obtain, and a study of the conditions of infection of these 
grasses by the Uredo-form of Puccinia dispersa , the Rust-fungus so 
common on certain species of them. 
The details of the results will, I hope, appear in due course, but 
some points of interest may be summarized now. 
The uredo-spores germinate at all temperatures between about 
10-12 0 C. and 25-27-5° C., which may be considered the minimum 
and maximum cardinal points; the optimum is about 18-20° C., and 
many failures in infection were found to be due to the fact that the 
leaves of the grass may be at temperatures above the maximum. Uredo- 
spores in water frozen for ten minutes into solid ice germinated on 
thawing, but freezing for two hours seems to kill them. 
Infection experiments show that spores originating on a given 
species — e.g. B. mollis — easily infect that species, but not necessarily 
another species, even if closely allied, and indeed may not infect all 
varieties of that species. Thus spores from B. sterilis easily infect 
B. sterilis and the closely allied B. madritensis , but not B. mollis or 
its allies B. secalinus , B. arvensis , &c., and not even the more closely 
