300 BOOKS AND CURRENT LITERATURE 



and ice crystals apparently grow into the tissues through the larger 

 openings and so start crystallization within. Freezing first occurs in 

 localized areas, with the filling of the gas spaces with liquid. Another 

 important point here emphasized is that frozen cells in leaves of cab- 

 bage, etc., are stimulated to later growth and the development of 

 enormous tumors "similar to those shown in pathological conditions, 

 but without the presence of bacteria." (It is remarkable that plant 

 pathology seems to be generally regarded as dealing exclusively with 

 diseased conditions due to bacteria, fungi, etc., as if diseases not 

 related to the commonly studied parasites were not accompanied by 

 pathological conditions! To the reviewer these intumescences that 

 follow partial and local freezing are just as truly pathological phe- 

 nomena as they would be if they happened to result from bacterial 

 invasion.) This hypertrophy is considered as perhaps primarily 

 related to a partial precipitation of the protein content of the cells, as 

 a result of freezing, and "this precipitation results in an increase in the 

 permeability of the cells to water, and in [an increase in] the abilit}'- 

 of the cells to hold sugars." The tumor cells show lower values of the 

 freezing-point lowering than do the rest of the leaf cells, but they 

 contain more sugars, perhaps in chemical combination and conse- 

 quently not effective to lower the freezing-point. Hydrogen-ion con- 

 'centration is increased in the tissue liquids as a result of non-lethal 

 freezing, and this, — ^together with alterations in salt concentration,— 

 is regarded as a main primary cause for the precipitation of proteins 

 and the subsequent tumefacient hypertrophy. Apparently hardening 

 (by exposure to low, but nonfreezing, temperatures) is effective by 

 altering the proteins so that they will be less readily precipitated on 

 freezing. The effects of desiccation, freezing, and plasmolysis are con- 

 sidered to be similar, in that all these processes cause changes in the 

 hydrogen-ion and salt concentration." This last statement is of 

 special interest as a principle of general physiology; the similarity of 

 these influences (and poisoning, as by bacterial excretions and other 

 materials, as the author might as well have added) becomes more and 

 more emphasized from many points of view, as physiology progresses. 

 — B. E. Livingston. 



Climate and Plant Growth. — Investigations by Sampson^ were 

 undertaken for the purpose of comparing climatic requirements of 



1 Sampson, Arthur W. Climate and plant growth in certain vegetative asso- 

 ciations. U. S. Dept Agric. Bui. 700. 1918. 



