Observations and Experiments on Cereal Rusts. 149 
(c) Hibernation through sori in seed. 
Reference has already been made to the experiments con- 
ducted by Hungerford* with rusted grain of wheat. In the 
summer of 1921 while carrying on some work on the specializa- 
tion of black rust, some seedlings of Couch grass were raised 
from healthy as well as from badly rusted grain collected in the 
autumn of 1920. It was found that rusted grain invariably gave 
healthy plants, and there was no trace of rust even on plants 
as many as ten weeks old. Only those seedlings which were 
artificially inoculated developed the disease, and the controls 
never became rusted. The writer is in complete agreement with 
the view expressed by Hungerford, that propagation of rust 
through infected seed is improbable. 
(a) Aecidium on barberry and fresh outbreaks of rust. 
Recently Stakman and Piemeiself have stated that they are 
in doubt as to the importance of the overwintering of the uredo- 
stage on grasses, but have remarked that barberry may be 
important at least locally. 
Similarly Freeman and Johnson} have observed that aecidio- 
spores may be sufficient in number (in spite of their short 
viability) to cause epidemics on grasses. 
Broadbent§ has pointed out that there is a plentiful distri- 
bution of the common barberry in the counties of Carmarthen- 
shire, Cardiganshire and Pembrokeshire, and that black rust on 
wheat is generally distributed over the same area. In all other 
parts of the British Isles he states that black rust is scarce. 
Lastly Lind|| and Giissow{] have made an important state- 
ment that the gradual extermination of barberry since 1903 has 
brought about a great decrease in the severity of black rust in 
Denmark. 
The complete absence of black rust in the summer of Ig2r at 
the University farm has been noted above but it was found on 
Couch grass and barley at a farm near Cambridge in the same 
season. This farm was known to have a few plants of barberry 
in the hedgerow which were kept under observation from the 
beginning of spring. Ripe aecidia were noticed on the barberry 
on the 6th of June and till then there was no trace of black rust 
although the standing crop of barley had plenty of P. simplex 
* Hungerford, C. W., Journ. Agr. Res. xIx, p. 257 (1920). 
t Stakman, E. C. and Piemeisel, F. J., Journ. Agr. Res. x, p. 429 (1917). 
{ Freeman, E. M. and Johnson, E. C., U.S. Dept. Agr. Bur. Plant. Indus. 
Bull. p. 216 (1911). 
§ Broadbent, W. H., Journ. Minis. Agric. xxvutI, p. 117 (1921). 
a Po J., Danish Fungi as represented in the herbarium of E. Rostrup 
{] Giissow, H. T., Phytopathology, m1, p. 178 (1913). 
