Tg15] CURRENT LITERATURE 161 
poisoned pea plants make to reproduce themselves. ... . In the greater 
strengths of such poisons’as zinc and copper sulphate [sic] root growth is 
checked from the outset, but usually a very little shoot growth is made, and 
one frequently obtains ridiculous little plants about an inch high bearing 
unhappy and diminutive flowers, which are occasionally replaced [succeeded 
e 
apprehend that the source and fount of all this woe is a lowered permeability 
for water, with a resultant development in which lack of water is the limiting 
factor. This is also the case with the plants of Pisum, Phaseolus, and Zea 
described on p. 18; the high concentration of copper sulphate here employed 
totally inhibited ott development, but the resultant strong growth of tops, 
instead of being due to “stimulation of the shoots by some physiological process 
or other,”’ as the author thinks, is exactly what we find wherever inhibition of 
root development, however caused, permits the utilization of the foodstuffs 
present in the seed solely in the development of aerial parts. The most 
remarkable passage in the book, however, is undoubtedly that on p. 27, in 
which we are told that ‘‘so long as the solution of copper salts is dilute enough, 
the absorption layer of the root, acting as a semipermeable membrane and 
upheld by the resistant na toplasm, is able to keep the copper out of the 
plant and to check its toxicity. As soon as a certain limit is reached the 
copper exercises a corrosive influence upon the outer layer of the root whereby 
its functions are impaired, so that it is no longer able efficiently to resist the 
entry of the poison. As the concentration increases it is easy to conceive that 
the harmful action should extend to the protoplasm itself.” Just what this 
“absorption layer’? may be the author does not tell us; it seems not to be 
protoplasmic, and inasmuch as it seems to combine the active réle of Horatius 
at the bridge with the more passive function of the Holland dikes, physiologists 
will regret that we are told no more of its origin, functions, and relation to 
cell wall and protoplasm than has been quoted. 
That the book is exceedingly disappointing will be obvious from these 
quotations. Physiologists have been awaiting the appearance of a résumé 
of the whole subject of toxic action which would bring together the extensive 
eae. of the older literature and unify and explain them in the light 
of the new knowledge of the nature and behavior of the protoplasmic mem- 
brane. The author who successfully undertakes the task must have kept 
abreast of the literature in many fields; with the tremendous advances made 
in physical chemistry and in our knowledge of the colloids, no less than with 
the work done directly with the subject in hand, for most help will come from 
the literature of these related fields. It is just here that Miss BRENCHLEY 
has failed; her book merely collects a mass of observations which it will be the 
task of some future physiologist possessing wide training and a modern point 
of view to organize and explain. 
There are various minor omissions and slips of the pen. Thus while 
formulae for two nutrient solutions are given on p. 13, we are nowhere told, 
