168 BOTANICAL GAZETTE [FEBRUARY 
that such treatment leads to an increase in ammonium salts, but it is not shown 
that such an increase of ammonium salts, by furnishing more nitrogen, will 
cause such a rise in yield, nor that the beneficial effects are not due to any 
one of half a dozen other possible changes in the soil. BoLtey has some evi- 
dence that in the wheat lands of North Dakota such treatment increases yield 
by killing certain parasitic fungi. 
Since SCHREINER and his collaborators have shown that many organic 
substances, some toxic and some stimulative to higher plants, are produced 
by decomposition of the organic débris of the soil, it is possible that the effect 
here is due to accumulated organic substances of one sort or another brought 
about by unbalancing the soil flora or fauna. Our Bureau of Soils has also 
collected much other data showing the extreme complexity of the problem 
of fertility and the danger of reasoning too directly from the mineral nutrient 
theory. 
There are a number of minor defects involving form of statement, degree 
of emphasis, and errors of fact (certain to creep into the most carefully written 
book) that deserve notice. Only a few of these can be mentioned. Con- 
sidering the idea RussELL wishes to convey, it seems better to use the more 
specific term “mineral nutrient” than the word “food.” The author con- 
siders that non-available water is such because of the concentration (osmotic 
activity) of the salts in it (p. 104). Known facts in this matter indicate 
— that the resistance to absorption is capillary. Rendering soil toxins 
us by oxygenating or by filtering over fine powders is described as 
peciptatng them (p. 133), whereas the process in the first case is oxidation 
and in the second adsorption. No mention is made of the importance of 
surface —. in soil phenomena, though it plays an important réle in floccula- 
tion, deflocculation, localization of solutes, etc—WILLIAM CROCKER 
The evolution of plants 
This little volume by Scorr? belongs to a not unfamiliar category, but 
it is rare to find a work on evolution written by an eminent morphologist and 
a distinguished paleobotanist. This constitutes such an unusual equipment 
that although the work under consideration is ges in its appeal, the mode 
of treatment is of interest to the professional botani 
The author at the outset draws a happy Petal ives the value of our 
knowledge of fossil forms as a key to the course of plant evolution in general 
and the history of cultivated varieties of plants in relation to their derivation 
from wild ancestors. In a second chapter the characteristics and statistics 
of the angiosperms are dealt with, special emphasis being laid on the external 
organization of the angiospermous flower. In the third chapter the gymno- 
2Scort, D. H., The evolution of plants. pp. 256. figs. 25. New York: Henry 
Holt & Co. 1912. 75 cents. 
