PLUM DISEASES 379 
winter-over, are viable in the spring, and can cause new infec- 
tions after several months’ rest. © 
After the uredospores have been developed they are replaced 
in the sori by other spores, known as teliospores. These follow 
closely the development of uredospores; they are said to appear 
in five to twenty days after the uredospores. The teliospores 
germinate in the spring, producing small, light sporidia which do 
not infect the stone-fruits, but must go to species of Anem- 
one, Thalictrum and Hepatica, all common wild flowers. 
On any of these flowers germination and infection occur. The 
mycelium developed in these hosts lives over until spring, when 
fruiting sori-bearing eciospores are produced. Just preceding 
these bodies sterile structures known as pycnia are developed 
on the upper surface of the leaves as black dots. The mycelium 
in the leaves may live over in these wild flowering plants for 
several years in succession, so that the stone-fruits are not 
absolutely necessary to the perpetuation of the fungus on these 
wild flowers. In this connection, however, it should be noted 
that the wild flowers already enumerated are necessary to the 
perpetuation of the fungus on stone-fruits. The sciospores 
developed on Anemone and others are wind-borne to the plum, 
where infection occurs on the leaves. Within three weeks after 
inoculation uredospores are mature and ready for summer dis- 
seminationof the fungus. Plum-trees are not generally attacked 
until sometime after the month of June, except in Australia, 
where infection occurs in February and March. 
Control. 
In those sections where plum-rust is troublesome it is probable 
that spraying will reduce the injury. The treatment as advised 
for peach leaf-curl, that is, spraying before the buds open with 
some standard fungicide, is recommended. In southern Cali- 
fornia it appears that early fall pruning performed to such an 
extent that fall growth is stimulated is not advisable. The 
difficulty involved lies in the fact that such foliage remains alive 
