1922] CURRENT LITERATURE 417 
fall, together with the length of the average frostless season, are given in readily 
accessible form, the resulting tables covering thirty-three pages. These data 
are plotted as isoclimatic lines on the map of the —_ States. Among the 
factors thus tabul sii and mapped are: temperature efficiencies for the 
frostless season expressed as (1) ae indices, a expotential indices, and 
(3) physiological a absolute temperature maxima and minima; average 
precipitation for the frostless season together with the number of rainy and dry 
days for same; normal annual precipitation; atmospheric evaporating power; 
ratios of precipitation to evaporation ; aqueous vapor pressure; relative air 
humidity; wind velocity; sunlight; and moisture temperature indices. 
It is recognized that there are decided difficulties in establishing correla- 
species, growt 
forms, and vegetational areas, but even here the efforts of the authors have 
under which various plant communities and plant species have developed. 
A very decided addition to our knowledge 6f the exact conditions that probably 
determine general vegetational areas is also provided in the plotting of the 
comparative ranges and intensities of twelve leading climatic conditions for 
nine sag areas, for Bie life-zones of Merriam, and for over thirty plant species. 
Th ting of text and maps characteristic 
o 
of the publications of the Coie Institution of Washington, and seems reason- 
ably free from errors of typography and in the use of specific names. It will 
be indispensable to all ecologists who wish to take account of climatic factors, 
and will become increasingly useful as increasing knowledge permits more 
accurate interpretation of such factors and their closer correlations with the 
resulting displays of plant life—Gro. D. FULLER. 
atomy and biology of gymnosperm leaves.—While there have been 
several investigations of leaves in various groups of gymnosperms, there has 
been no comprehensive study of the entire line. Consequently, a recent work 
by FEustex” will be welcomed by those who wish to find, in compact form, a 
survey of the literature of the subject. The author states frankly that his 
work is only a summary of the literature, not an investigation; but his obser- 
vations, , especially along biological lines, and the comparative presentation of 
anatomical features are suggestive. The various orders are treated separately. 
Cxcibdeajeits the term Pteridospermae is used for this order. 
The mode of treatment is similar in the other orders. In general appearance 
the leaves are fernlike, but the internal structure shows a mixture of fern and 
%° FEUSTEL, Herm., Anatomie und biologie der Gymnospermenblatter. Beih. 
Bot. Centralbl. 38:177-257. 1921. 
