04 
less still beset with difficulties, both in regard to the 
permanence of the rust-resistance, and to the fact that 
a wheat, which is resistant to one form of rust may be 
equally susceptible to another. Further, wheats which 
are resistant, say in England, are not necessarily so in 
India or Australia. It has been essential therefore for 
each country to establish its own rust-resistant varieties 
of wheat. 
Many of our common garden plants are liable to 
attacks by different rust fungi. The Mint rust caused 
by Puccinia menthe is one of the most prevalent of these 
in some districts. In this example the three forms of 
spore appear in succession, and there is no intervention of 
a second host plant in the life cycle of the rust. In the 
spring diseased plants send up shoots which are often 
swollen and distorted, and bear the cluster-cups of the 
fungus. ‘lhe aecidiospores are liberated as a bright yel- 
low dust and infect the leaves of healthy shoots so spread- 
ing the disease. The pustules produced by this infection 
are brown in colour and are scattered, as minute dark ' 
spots, over the leaves. Uredospores arise from these 
pustules throughout the summer, and towards the end of 
the season teleutospores are produced from similar disease 
spots. The teleutospores remain in a resting condition in 
the soil for some months, but germinate in the early 
spring giving rise to sporidia, which infect the young buds 
on the underground stem. Such infected buds are not 
killed outright by the fungus, but grow out to produce 
the distorted shoots bearing the aecidiospores, described 
above. It has also been shown that once the underground 
stem is infected, the fungus lives there perennially and 
grows into the young buds as they are formed. This 
renders the disease all the more difficult to eradicate. 
Indeed, the best plan is to destroy all infected material 
and only use for planting, rhizomes known to be free from 
the fungus. Care should also be taken to prevent infec- 
tion by teleutospores from soil which has grown diseased 
plants. 
As an example of a rust caused by a fungus with a 
simpler life history, the Hollyhock rust produced by 
Puccinia malvacearum may be considered. This disease 
occurs on a large number: of the members of the Mallow 
family; it is widely distributed throughout the world and 
is abundant in this country, both on wild mallows and on 
