[Vor. 1 
314 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
designated as B. oleracee Harrison, and B. omnivorous Van Hall, 
and that it may possibly be identical also with Potter's B. 
destructans. By many tests Jones has shown that this organism 
secretes an enzyme which causes the disintegration of the host 
cells by dissolving the middle lamella, which, according to the 
majority of investigators, is composed of salts of pectic acid. 
This author has further isolated from pure cultures of the or- 
ganism an extra-cellular enzyme, which he designated pectinase, 
that destroys the middle lamella of the cells just as does the 
erowing organism. Jones, therefore, considers this enzyme 
responsible for the disintegrating action of the bacillus. 
In my own work I shall adopt the nomenclature used by Jones 
(29, 30) and Ешег (21), namely, employing pectinase as the term 
to designate the enzyme inducing coagulation of a pectin solu- 
tion and also the hydrolysis of calcium pectate, or pectinate. 
Methods.—In order to determine the effect of the fungus on 
the middle lamella I have used two methods, (1) a microscopic 
study of the effect of the fungus on the host cells, and (2) a 
study of the effect of the organism on the substances (isolated 
from the host) which are commonly reported to be constituents 
of the middle lamella. The first method has been discussed 
above and may be dismissed here by stating that it yielded no 
positive evidence that the fungus dissolves the middle lamella. 
By the second method the problem was studied by isolating pec- 
tin from the host and studying the effect of the fungus on it 
and also on its salts, as, for instance, calcium pectinate. 
Pectin was isolated from plums by the following method: 
Thoroughly ripe fruits were steamed—no water being added, the 
juice filtered off and treated with Almen’s reagent! (to precipi- 
tate the protein) and with a very dilute solution of oxalic acid 
(to precipitate the calcium). It was found that under these 
conditions neither а calcium nor a protein precipitate was thrown 
down either by Almen’s reagent or the oxalic acid, and this pro- 
cedure, therefore, was deemed unnecessary and was abandoned. 
The plum juice was carefully filtered through a Buchner filter 
1Abderhalden, E. Handbuch d. biochem. Arbeitsmethoden 2: 391-92. 1910. 
Almen’s tannic acid solution is made by treating 4 grams of tannic acid with 8 cc. 
of a 25 per cent solution of acetic acid, and making up to 190 сс. with 40 or 50 per 
cent alcohol. 
