208 THE AMERICAN NATURALIST. [VoL. XXXIII. 
did not vary in any marked degree from the growth and spore devel- 
opment of dry spores. 
Dr. Erwin F. SMITH: Sensitiveness of Certain Parasites to the Acid 
Juices of the Host Plants. — The author presented a tabular statement 
of the results obtained by inoculating acid nutrient solutions with 
bacteria parasitic to plants, e.g., Pseudomonas campestris, Ps. phaseoli, 
Ps. hyacinthi, Ps. stewarti, Bacillus amylovorus, B. olee, etc. He was 
led to these studies by observing that the three yellow plant parasites 
first named spread very slowly through the parenchymatic tissues of 
their host plants. This is true in the field and in the greenhouse, 
and it also occurs when enormous numbers of the organism are in- 
jected into the parenchyma by means of hypodermic syringes. To 
fully realize the slow progress of these diseases they should be com- 
pared with such rapid diseases as pear blight, the brown rot of the 
potato, or the soft white rot of hyacinths, which often destroy 
large portions of the host inafew days. ‘Two of these yellow organ- 
isms are vessel parasites, their entrance into the plant being favored 
by the alkaline juice of the ducts. In all three the restraining influ- 
ence was believed to be, in great part, at least, the acid juice of the 
parenchyma. The detailed experiments confirm this view and show 
that there is a very wide difference in the susceptibility of bacteria 
to plant acids. All of the solutions were titrated with > NaOH and 
phenolphthalein, so that their exact acidity is known. Those who 
wish details are referred to a forthcoming bulletin on the pathogenic 
properties and life history of Ps. Ayacinthi, of which this paper will 
form a part. 
Dr. CARLETON C. Curtis: Further Observations on the Relations 
of Turgor to Growth. — Experiments were undertaken to determine 
(1) how soon growth would be renewed after a change in the concen- 
tration of the nourishing solution, and (2) to measure the turgor force 
at the moment of renewed growth. Three species of fungi were used 
— a Penicillium, a Mucor, anda Botrytis. These plants were grown in 
nourishing solutions and in the same with addition of 4, 9, 14, and 
20 per cent nitrate of potash. Penicillium grown in the nourishing 
solution had a turgor force of 7.5, nitrate of soda being used as a 
plasmolyzer; when grown in 20 per cent nitrate of potash, it had a 
turgor force of 42.5. When transferred from the nourishing solution 
to the 20 per cent solution, growth was stopped from 8 to 12 hours. 
_ At renewal of growth the turgor was found to be normal for the 20 
