CRYPTOGAMS 317 
C. Rusts 
Marteriay. — A leaf of wheat affected with red rust; a leaf or a stalk 
with black rust. Some barberry leaves with yellowish pustules on the 
under side, which under the lens look like clusters of minute white corollas. 
These are popularly known as “cluster cups.’”’ As the spots on barberry 
occur in spring, the red rust in summer, and the black rust in autumn, 
gather the specimens as they can be found, and preserve for use. 
The orange leaf, or brown, rust (Puccinia rubigo-vera) is more common 
in some parts of the country than the ordinary wheat rust (Puccinia 
graminis), but the two are so much alike that the directions given will 
do for either. If the orange leaf-rust (so named from its color, and not 
from any connection with orange leaves, the logical relation of the words 
being orange leaf-rust, and not orange-leaf rust) is used, the cups and 
pustules should be looked for on plants of the borage family — comfrey, 
hound’s-tongue, etc. The orange leaf-rust of apple is caused by a fungus 
which will serve to illustrate the same class of parasites. 
The ‘“teleuto”’ stage of this will be found on cedar 
trees, in the excrescences commonly known as “cedar 
apples’’; the “cluster cups’’ on the leaves of apple 
and haw trees affected with the disease. 
359. Red rust. — Uredo stage. Examine 
a leaf of ‘‘ red rusted’ wheat under the lens, 
and notice the little oblong brown dots that 
cover it. These are clusters of spore cases, 
and are the only part that appears above the 
surface. Viewed under the microscope, the 
red rust will be seen to consist of a mycelium 
(see Fig. 452), which ramifies through the 
tissues of the leaf and bears clusters of single- 
celled reddish spores that break through the igs. 450, 451, 
epidermis and form the reddish brown spots Leaf of wheat af- 
and streaks from which the disease takes its aig eae 
name. These spores, falling upon other eekaise ke 
leaves, germinate in a few hours and form side of leaf; 451, 
new mycelia, from which, in six to ten days, wader bide: 
fresh spores arise. Formerly this was thought to complete the 
life history of the fungus, to which the name of Uredo was 
given. It isnow known, however, that the red rust is merely a 
451 
