[Vol. 10 



8 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



pressed the opinion that the species described by Appel, Harri- 

 son, and Pethybridge and Murphy should be referred to van 

 Hall's Bacillus atrosepticus. The argument advanced by this 

 investigator is most logical, but attention is called to the fact 

 that he did not carry out comparative studies using the several 



"species" in question. 



Rosenbaum and Ramsey ('18) contributed the results of some 

 studies upon the influence of temperature and precipitation on 

 the blackleg of potato. 



Ramsey's ('19) studies of the viability of the potato blackleg 

 organism led him to believe that the pathogen does not live in 

 the tubers left in the field over winter. He expressed the further 

 conclusion that unless the potato seed were infected at planting 

 time there was little chance that the uninjured plants would con- 

 tract the disease. 



Artsch wager's ('20) researches upon the pathological anatomy 

 of potato blackleg form a new contribution to our general knowl- 

 edge of this disease. He studied only blackleg plants grown in 

 the arid regions of western Colorado. The affected plants ex- 

 amined by him were found to show an increase in strongly lig- 

 nified vascular tissue and a transformation of part or most of 

 the parenchyma cells of the cortex and pith into sclerids. This 

 investigator also discovered that protein crystals occurred in 

 great abundance in all organs of plants affected with the black- 

 leg disease, especially in the leaves, while under normal condi- 

 tions protein crystals have been observed only in the peripheral 

 cell layers of the cortex of the potato tubers. 



Jennison's ('21) abstract, "Bacillus atrosepticus van Hall, the 

 cause of the blackleg disease of Irish potatoes" was based on the 

 investigations carried out in large part in 1916 and 1917, here 

 reported upon in detail. While the group number as published 

 by the writer at that time differs in respect to the last 3 digits 

 from that of Morse ('17), it agrees throughout with that assigned 

 by Shapovalov and Edson ('21). The last-named investigators 

 contributed one of the most important of the recent accounts 

 of the disease under discussion. They showed that the potato 

 blackleg disease prevailed in the irrigated districts of the West, 

 and that the causal agent was a Bacillus, which they concluded 

 was "identical with Bacillus phytophthorus Appel in all the 

 essential characteristics considered in determining bacterial spe- 



