Pole Evans . — The Cereal Rusts. 
449 
It was first distinguished as a single species, with very distinct morpho- 
logical and biological characteristics by Eriksson and Henning ( 16 ), and 
a few years later Eriksson divided the old P. rubigo-vera , DC., into seven 
additional forms, so that to-day under P. rubigo-vera , DC., he includes : — 
1. P. glumarum (Schm.), Erikss. and Henn. 
The Yellow rust. Aecidium unknown. 
2. P. dispersa , Erikss. 
The Brown rust of the rye. Aecidium on Anchusae. 
3. P. triticina , Erikss. 
The Brown rust of wheat, xA.ecidium unknown. 
4. Sy mphyti- Bromoru m . Miill. 
The Brown rust of Bromes. Aecidium on Symphytum. 
5. P. agropyrina , Erikss. 
On Triticum repens. Aecidium unknown. 
6. P. holcina , Erikss. 
On Holcus lanatus, H. mollis. Aecidium unknown. 
7. P . Prise ti, Erikss. 
On Trisetum Jlavescens. Aecidium unknown. 
8. P. simplex (Kcke.), Erikss. and Henn. 
The dwarf rust on Hordeum vulgare. 
Eriksson ( 9 ) divides P. glumarum into five specialized forms. 
1. P. glumarum Tritici, Erikss. 
In which uredospores from wheat will only infect wheat, but not 
barley or rye. 
2. P. glumarum Hordei , Erikss. 
Uredospores from barley will only infect barley, not rye or wheat. 
3. P. glumarum Secalis , Erikss. 
Uredospores from rye infect only rye, not barley or wheat, although 
Eriksson says he once got a feeble success from rye to wheat, and therefore 
is inclined to regard his form as ‘ nicht scharf fixiert ’. But we need further 
experiments on this point before it can be regarded as such. 
4. P. glumarum Elymi , Erikss. 
Uredospores from Elymus arenarius , L., will not infect either wheat, 
barley, or rye. 
5. P. glumarum Agropyri , Erikss. 
Uredospores from Agropyrum repens , Beauv., will not infect rye, 
wheat, or barley. 
P. glumarum is also found on the following Bromes : — -Bromus 
adoensis , asper , arvensis mollis , secalinus , sterilis , tectorum. 
The Uredo stage of P . glumarum is readily distinguished in the field 
by its bright yellow colour, sulphur to pale cadmium. The pustules have 
a great tendency to run in long rows up and down the leaf, sometimes 
producing a disease spot as much as 70 mm. long, but this is by no means 
