DECEMBER 31, 1897.] 
if a specimen is mounted in olive oil. The ex- 
eretion of water from the cells soon begins and 
a cylinder of ice is formed about the filament. 
As a result of the work upon unicellular 
structures in many organisms, it is found that 
the freezing may be accompanied by the forma- 
tion of ice in the cell, external to the cell mem- 
brane or in both places. In either case it is 
accompanied by a more or less complete separa- 
tion of the water from the plasma. The ex- 
posure of tissues with strongly developed walls 
to low temperatures was accompanied by the 
excretion of ice into the intercellular spaces, 
followed by the formation of ice both here and 
in the cell. Not all the cells of a plant exhibit 
the same resistance to cold. A temperature of 
a few degrees below zero Centigrade may freeze 
a leaf while the guard cells and hairs will re- 
main intact. These cells are likewise highly 
resistant to heat and other agencies, as Leitgeb 
has previously demonstrated. 
The question as to the death of a plant upon 
freezing or consequent thawing has engaged the 
attention of a large number of workers. Mo- 
lisch’s results prove that generally the death of 
a plant is due to the direct action of cold upon 
the plasma, and that the consequent thawing 
does not matter whether slow or rapid, in air 
or water. To this generalization an exception 
is offered by the experience of Muller-Thurgau, 
who found that frozen fruits of the apple and 
pear were not destroyed if thawed slowly, a 
fact long known in household practice, and the 
experiment of Molisch with Agave americana, 
which behaved in asimilar manner. These ex- 
ceptions, of course, rest upon the provision that 
the temperature has not fallen below a certain 
limit. 
The death of plants from temperatures above 
the freezing point may result from disturbances 
of the metabolic processes or the transpiratory 
activity. In the latter instance the ‘frosting’ 
of a plant is due to the decreased osmotic ac- 
tivity of the root hairs under low temperatures, 
and wilting of the leaves consequent upon an 
insufficient supply of water. Dr. Molisch is 
mistaken in attributing the origin of this idea 
to Krabbe, as the principle has been known for 
many years, although its detailed application 
was first exploited by Krabbe. 
SCIENCE. 
1008 
Among the plants which are killed by low 
temperatures above freezing point, the most 
delicately responsive are Hpiscia discolor Hook., 
Sanchezia nobilis Hook., Eranthemum tricolor 
Nichols., E. coupert Hook., E. ignewm Linden., 
Anectochilus setaceous Blume. The species in 
this list exhibit damage after exposure to tem- 
peratures 1.4° C. to 3.7° C. for periods of 18 to 
100 hours. Begonia stigmatosa, B. scandens, 
Behmeria argentea Linden, Tradescantia dis- 
color, T. zebrina, and Euphorbia splendens, 
Ficus elastica, Gloxinia hybrida, Tropzolum majus, 
are examples of a numerous class which are in- 
jured by longer exposure to the same tempera- 
ture. It is to be seen that Molisch’s carefully 
attained results sustain the contention of Goep- 
pert and Miuller-Thurgau that death from freez- 
ing is due to the formation of ice or to the 
direct influence of cold, and not to the pro- 
cesses of thawing as maintained by Sachs. The 
formation of ice entails the excretion of water 
from the protoplasm, and the great and rapid 
loss of the fluid results in the architectural dis- 
integration of the plasma. The disintegration 
may be hastened by the poisonous action of 
concentrated cell-sap remaining. 
So far as the results are at hand, itis to be said 
that the excretion of water by cells at low tem- 
peratures is not only a physical reaction, but this 
action has become under the direction of the 
protoplasm a protective adaptation. A second 
adaptation consists in the smallness of the cell. 
D. T. MAcDOUGALL. 
SOCIETIES AND ACADEMIES. 
BOSTON SOCIETY OF NATURAL HISTORY. 
THE Society met December 1st; thirty-five 
persons present. Professor N. 8. Shaler, in dis- 
cussing Aeolian deposits in relation to the forma- 
tion of river valleys, gave the result of his ob- 
servations in Utah and Montana. Along the 
Ruby river, where the vegetation is dense and 
the soilrich, the loess is held and the valley 
built up. In Montana below 7,000 feet the 
vegetation is thin and insufficient to inhibit. 
Mr. A. W. Grabau showed some fossils from 
the upper Devonian of western New York, and 
gave the views taken by various investigators 
as to the nature of Conodonts, since their dis- 
covery by Pander in the Silurian and Devonian 
