146 BOTANICAL GAZETTE [ AUGUST 
A brief discussion of the ionization of gases and of solutes in solution 
opens the way for a very satisfactory presentation of the general subject of 
osmosis, wherein the osmotic pressure of non-electrolytes, electrolytes and col- 
loids is treated, and the means and methods of measuring and calculating the 
pressure are set forth with appropriate formulas. 
Having laid a foundation in the physical, the author proceeds to the still 
more difficult physiological. To this part nearly a hundred pages are given. 
Only a few of the more striking topics can be mentioned here. Plasmolysis 
is shown to be not a matter of simple interpretation, as one would infer from 
literature generally, but a thing to be judged only after the permeability of 
the protoplasmic membrane is known. To determine the permeability various 
tests are detailed. The action of the protoplasmic membrane and the main- 
tenance of turgidity in spite of permeability are two of the most interesting 
because most difficult theoretical discussions. It is evident that the author 
inclines to the solvent theory as applied to the action of the membrane in 
osmosis. In the chapters on the absorption and transmission of water and 
solutes, the means of lifting the sap to the tops of trees, and the means of 
éxudation from water-pores, nectaries, etc., receive due consideration. These 
most difficult questions are not, as is too often the case, dismissed with the 
statement that there are no satisfactory explanations, but carefully and 
clearly the principal experimental results are recorded, their bearing pointed 
out, and their insufficiency noted. The pumping action of osmosis and the 
tensile strength of water are given as both probable means in the lifting of 
sap to great heights; while a change in the permeability of the protoplasmic 
sac is given as the possible cause of the beginning of excretion by water- 
pores and nectaries. 
The last chapter represents in large measure original work by the author. 
Here are summarized his well-known experiments on the morphology of algae 
as influenced by the osmotic pressure of the surrounding medium. The work 
f Loeb, Massart, Rothert, and others, on the effect of osmotic pressure on 
irritability and in inducing parthenogenesis finds appropriate mention. 
In the book as a whole there is little to criticise adversely.and much to 
praise. Possibly the author pushes the theoretical a little too far sometimes, 
as, for example, in his explanation of the rise of a solution in a thistle-tube 
used as an osmometer. But it is better to state an insufficient hypothesis 
than to ignore all. In the reviewer's opinion one of the merits of the book is 
its abundance of theories clearly and boldly stated, while at the same time it 
points out the strength and weakness of each. 
Pedagogically the treatment is excellent. The parts are well arranged, 
everything is interesting, a basis for the physiological is laid in the physical, 
there are copious citations of literature, and there are many suggestions as to 
problems for research. In the opinion of the reviewer Dr. Livingston has 
produced an excellent treatise. — FREDERICK C, NEWCOMBE. 
