68 
MILDEWS, RUSTS AND SMUTS 
first. The enclosing wall or peridium is usually whitish, 
with a torn edge that curves outwards when mature. The 
aecidia are usually produced in groups or clusters on pale 
spots. The sori of uredospores and teleutospores usually 
appear under the form of small pustules, but in some in¬ 
stances when the teleutospore sori are produced on the stem, 
as on the broad-bean, the sori form long, blackish, crust¬ 
like patches. The teleutospores have a single germ-pore 
at the tip or apex. 
HEMILEIA 
The outstanding feature of this genus is the emergence 
of the sori of uredospores only through the stomata of the 
host-plant. In those species where the uredospores are 
crowded, the free, convex portion of each spore is warted 
or ornamented in some way, whereas those portions of the 
spores in contact with each other are smooth. When the 
sori are lax and the spores free from each other, they are 
warted all over. The teleutospores grow up in the centre 
of the uredospore clusters, and do not form independent 
sori. 
An introduced genus. 
MELAMPSORA 
Teleutospores forming flat, crust-like sori on leaves. 
The spores are closely crowded side by side, and are usually 
prismatic or polygonal from lateral pressure. The most 
conspicuous species occur on the fallen leaves of poplars, 
alders and willows. 
CRONARTIUM 
(Our only species produces its aeciaiospores on the bark 
of conifers (Pinus sp.). 
The uredospores and teleutospores grow on the under¬ 
surface of living leaves of the black currant. The teleu¬ 
tospores are cemented together into a slender hair-like 
outgrowth, which is surrounded at the base by the uredo¬ 
spores. As a rule myriads of the hair-like collections of 
teleutospores crowd the surface of the infected leaf. 
ENDOPHYLLUM 
The only British species grows on the living leaves of 
houseleek, and allied plants. The peculiar teleutospores 
are globose and produced in chains, and are enclosed in a 
peridium. The whole structure resembles in appearance 
an aecidium, and was so considered until germinating 
