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1898 | CURRENT LITERATURE 67 
resting place and food both to the butterfly and its offspring, the caterpillar. 
Just how far the term symbiosis is to be extended is becoming quite a ques- 
tion. If the above happy case of reciprocity is a true case of symbiosis, we 
must extend the application of the term to the conditions existing between 
certain groups of animals and plants. And if we extend it to this we shall 
be well on the way toward saying that the relations between plants and 
animals at large give us a gigantic illustration of symbiosis, There are many 
who are disposed to limit the term symbiosis to those more intimate relation- 
ships of organisms, cases of actually living together, the ““commensaux "” 
condition. As to how far the term shall be extended to those cases where 
organisms are dependent upon each other for a brief period, mutually or 
otherwise, becomes a question of degree rather than content.—O. Wa Mas 
AN IMPORTANT contribution to the bacteriology of plant diseases has been 
made by Dr. Erwin F. Smith ® in a study of brown rot in various cruciferous 
plants, especially in turnips, cabbage, and kale. A yellow, motile germ, of 
micrococcus-like appearance, has been isolated and its behavior in the labora- 
tory under various conditions tested. It is aerobic, produces no gas or acid, 
and forms no spores. 
In the cruciferous host it is chiefly found along the fibro-vascular bundles, 
especially in the vessels, and brings about a characteristic brown discolora- 
tion not shown when grown upon other media. A very interesting observa- 
tion was made in reference to its dispersion within the host. It travels along 
the vascular strands with readiness, but passes from one to another through 
the intervening parenchymatous layers with difficulty. The inhibitory con- 
dition appears to be due, in part at least, to the acidity of the parenchymatous 
Sap, the organism preferring the alkaline fluids of the bundles. 
Many interesting, novel and important details of the study cannot be even 
alluded to in this connection. The work has established beyond any seeming 
possibility of cavil another marked disease of plants caused by parasitic 
bacteria. 
The natural infection appears to be through the leaves, partly by the 
gnawing of worms and insects, and partly by the entrance of the germs 
through the water pores when root pressure fills them with sap. The disease 
'S apparently widespread, and of considerable economic importance. It does 
not break down the tissues to any marked extent, but beside producing a dis- 
Coloration it checks the growth, and often causes the leaves to yellow and 
drop, making the crop a failure. There is a curious omission of reference to 
the researches of Dr. H. L. Russell on this disease, some of which have 
already been published, as well as to those unpublished of which Dr. Smith 
2 PR egies es F.— Pseudomonas campestris (Pammel), the cause ofa eee 
dios: ‘iferous plants. Centr. f. Bakt. Par. u. Infekt. 3: 284-291, 408-486, col. pi. 0. 
