CHAPTER IV 
LIFE-HISTORIES OF OTHER UREDINALES 
Puccinia graminis. 
THE Biack Rust or “MILDEW” oF CORN. 
Another common Puccinia, whose life-history is of greater 
economic importance than that of P. Caricis, is the well known 
P. graminis, the Rust or Mildew of Corn. This species has its 
spermogones and ecidia on Barberry (Berberis vulgaris and 
Mahonia Aquifolium) and its uredo- and teleutospores on many 
species of grasses, especially on cultivated wheat. It must not, 
however, be assumed that any rust found on wheat is P. gra- 
minis; there are at least two other species common on the 
same host which, unless carefully examined, may be confounded 
with it, viz. P. triticina and P. glumarum, not to mention a form 
of P. coronata which sometimes also oécurs on cereals. For 
this reason these four species are now distinguished as the 
Black Rust, Brown or Orange Rust, Yellow Rust, and Crown 
Rust of corn, respectively. The uredo-stage of P. graminis is 
known as Red Rust. 
If one merely substitutes Barberry for Nettle and Wheat 
for Carex, what has been said about P. Caricis is true in all 
essentials of P. graminis. The differences are not in the life- 
history, but in ‘certain minor details of occurrence: e.g. the 
spots caused on the leaves of Barberry are small, round and 
red, while uredospores of P. graminis are most common on the 
leaves, and the teleutospores form long black striz on the 
