CURRENT LITERATURE. 
BOOK REVIEWS. 
Injury to plants by cold.' 
THE prominent and peculiar feature of this research lies in the direct 
observation, by the use of the microscope, of the phenomena of freezing. A 
specially constructed box, with triple walls for the non-conduction of heat 
and for receiving a freezing mixture, enabled the author to enclose his micro- 
scope where objects were frozen during observation. On freezing colloids, 
emulsions and solutions, Molisch found, as others had found before him, that 
water, on becoming ice, separated itself from the contained material; but 
Molisch’s microscope showed that the colloids formed a network of denser 
material, the emulsions formed a network of granules, and the solutions 
formed a network of concentrated or solid substance. Each of these net- 
works contained ice-masses in the meshes. On thawing, the network disap- 
peared guickly in some of the liquids, but only slowly in others such as starch 
paste, which is permanently altered by the freezing. 
The author next experimented with the freezing of living bodies, using 
- amoebee, hyphae of Phycomyces nitens, yeast, Spirogyra, and other alge, hairs 
of Tradescantia, and the guard cells of stomata. The results obtained here 
are directly comparable with those obtained with merely physical bodies. 
The protoplasm on freezing became a network of denser material, with lumps 
of ice in the meshes. The capillary filaments of Spirogyra and Phycomyces 
_ §ave up much of their water to the formation of an external ice mantle, and 
ice formed internally only at a temperature many degrees below zero, this 
being comparable with the well-known fact that ice forms in purely physical 
_ Capillary tubes only when the temperature is several degrees below zero. 
The guard-cells of stomata were found to form ice only when considerably 
below zero; and this phenomenon the author explains by the greater content 
of dissolved substance in these cells, and by their capillarity. 
In the next section of this monograph, Molisch seeks to answer the ques- 
__ tion as to whether plants die from freezing or thawing. Like Géppert, Sachs 
sag Miller-Thurgau, he has tested hundreds of plants by the slow and by 
€ rapid process of thawing, and like all but Sachs he finds, with the excep- 
*MoLiscu, HANs.—Untersuchungen iiber das Erfrieren der Pflanzen. Gustav 
Fi ischer, Jena, 1 : 
1897] ee ae ee 
