1896.] + The Bacterial Diseases of Plants. 631 
or by some bacteriologist, using pure cultures and plant 
juices which have been sterilized by filtration. 
Dr. Russell’s experiments’ were made a year earlier than 
than those of Wiesner and have the merit of being properly 
performed, i. e. with sterile juices and pure cultures so that 
the conditions under which the experiments were made 
can be reproduced by other investigators. They are, however, 
too limited in number to afford any basis for a general conclu- 
sion. He found that Canna juice, sterilized by filtration, 
exerted no appreciable germicidal effect on any of the following 
species: Kiel-water bacillus, B. lactis-ærogenes, B. coli-communis, 
B. megaterium, B. prodigiosus. Experiments with B. megater- 
ium, B. butyricus, B. coli-communis, B. pyocyaneus, and Strepto- 
coccus pyogenes, using as a culture medium root-pressure juice 
obtained under sterile conditions from the severed stem of lima 
beans and Pelargoniums led to a similar conclusion and to the 
enunciation of the following general statement: “vegetable 
cell juices, aside from their acid reaction, are entirely power- 
less against bacteria, and do not possess any germicidal pro- 
perties like the blood serum of animals.” 
- The old view that plants are not subject to the attacks of 
bacteria simply because their tissues are acid was shaken by 
the discovery that some bacteria grow very wellin acid media, 
and was thoroughly upset by the discovery that the juices of 
some parts of many plants are alkaline. In all probabil- 
ity plants like animals require a delicate balance between 
acid and alkaline and a continual change from one side to the 
other for the carrying on of the life processes. Three things at 
least are certain (1) It will not do to assume that all parts of a 
plant are acid because some part of the parenchyma shows a 
strongly acid reaction ; (2) It cannot be stated that any given 
microorganism will thrive only in alkaline media until this 
fact has been determined by direct experiment ; and (3) Many 
bacteria, perhaps all, are alkali producers and capable, if they 
can gain any foothold whatever, of slowly changing an un- 
suitable acid medium into one more alkaline and better 
adapted to their use. 
’ Russell: (9) Bacteria in their Relation to Vegetable Tissue. Thesis. Johns Hop- 
kins University. 1892, 8vo. p. 41. + - 
