MISSOURI BOTANICAL GARDEN BULLETIN T5 
of a diseased bud or scion. They are almost invariably trans- 
missible by cuttings and sometimes by the seed. One of the 
most destructive diseases of the peach in northern latitudes, 
peach yellows, is likewise transferable only by budding and 
grafting. Since no organism has been identifiable as causally 
related to the peach yellows, and since the chief symptom 
of the disease is a chlorosis, this disease is also tentatively 
grouped in the ‘‘variegation’’ or ‘‘chlorosis’’ category. 
Among the ornamental plants showing variegation will be 
included Evonymus, Ligustrum, and Abutilon. 
Plant Cancer or Crown-Gall of Plants—The most in- 
teresting bacterial disease of plants is generally con- 
ceded to be that known as crown-gall or plant can- 
eer. It is induced by a tumor-producing organism, Pseudo- 
monas tumefaciens. The attention of medical men has been 
directed to this plant disease particularly through some strik- 
ing analogies to human cancer as revealed more especially 
through the elaborate investigations of Doctor Erwin F. 
Smith, of the Bureau of Plant Industry, Washington, D. C. 
Doctor Smith has demonstrated that from the primary tu- 
mors produced by the bacteria, there originate certain infec- 
tion strands, and these are pictured as growing through the 
tissues of the host, inducing secondary tumor formation at 
greater or less distances from the primary infection. It is 
also believed that in a case where the primary infection is 
that of a stem and the invading strand enters a leaf, stem 
tissue will be produced in this secondary area. The causal 
bacterium is able to infect a great variety of host plants and 
frequently produces on apples, grapes, raspberries, and a va- 
riety of other cultivated plants certain characteristic swell- 
ings, usually at the base of the stem on the so-called crown ; 
hence the name crown-gall. The inoculations on Paris daisy, 
geranium, and tobacco will show, however, as is now well 
known, that aerial tumors are readily produced. Inoculated 
into the growing meristem of certain plants, such as the to- 
bacco, characteristic ‘‘embryomata’’ are induced. 
A Bacterial Disease of Cereals and Other Grasses.— 
A new bacterial disease of grasses and cereals has recently 
been studied in detail by Mr. H. R. Rosen, and some infection 
experiments showing the lesions and the course of this dis- 
