38 DISEASES OF TREES 



of bacteria, called B. Hyacinthi by Wakker, occur in the vessels, 

 and completely decompose the surrounding tissues. 



Under normal conditions the bacteria do not attack perfectly 

 healthy well-developed bulbs. Wounds of some kind are 

 necessary, which may be easily caused in transplanting the 

 bulbs, or the bulbs are previously attacked by filamentous fungi, 

 amongst which a species of Hyphomyces almost always accom- 

 panies the disease. In a damp situation the bacteria enter 

 the wound and cause it to putrefy. 



The wet-rot or " bacteriosis " of the potato, which generally 

 appears as an accompaniment of the decomposition of tubers 

 and stalks due to Phytophthora infestans, is also a disease 

 produced by bacteria.* 



The investigations conducted by Vuillemin a few years ago 1 

 have shown that Pinus halepensis is subject to a disease induced 

 by bacteria which may prove fatal to the tree. The first sym- 

 ptoms are that the stem and branches show small outgrowths 

 which gradually enlarge till they embrace the whole circum- 

 ference, when the portion of the tree situated higher up dies and 

 withers. When, as is usually the case, these swellings occur on 

 most of the branches, the tree succumbs altogether. 



The olive, also, suffers from a disease which is induced by a 

 species of bacterium {Bacillus Olece tuberculosis}? 



Lately a disease of apple- and pear-trees has been described 

 by J. Burrill, of Urbana, Illinois, under the name of " blight," the 

 cause of which, according to this investigator, is to be ascribed 

 to the invasion of a bacterium. The disease appears to bear 

 resemblance to the tree-canker produced by Nectria ditissima : 

 and as, in the case of this fungus, large numbers of small 

 gonidia resembling bacteria are produced in the cortex, it remains 

 to be seen whether this disease has not been erroneously ascribed 

 to a bacterium. 



1 C. R. Stances. November 26th, 1888, and December 3ist, 1888. 



2 L. Savartane, Les Maladies de I" 1 Olivier, Comptes Rendus, December 6th 

 and 2oth, 1886. 



* [It is extremely probable that in these and other similar cases the 

 minute bacteria travel into the tissues down the tubes of the filaments 

 (hyphse) of the fungus, feeding on the decomposing protoplasmic contents of 

 the latter. ED.] 



