1921] CURRENT LITERATURE 157 
to the literature, all serving to bring the work up to date. - It will continue 
to be a book which the plant physiologist and anyone interested at all in the 
chemistry of plant materials will want on his shelf.—S. V. Eaton. 
Soil alkali 
Harriss has written an excellent critica] little book on soil alkali. The 
author says: “It has been estimated that about 13 per cent of the irrigated 
land of the United States contains sufficient alkali to be harmful. This means 
that there are over 9,000,000 acres of land under present canal systems that 
are affected with alkali. There are many more million acres of alkaline land 
in the United States that do not lie under irrigation systems. Similar figures 
might also be given for other countries of this continent and for all other 
continents. The alkali problem is one of no mean importance to farmers, 
nor to any who are interested in the world’s food supply. 
In a strictly chemical sense the word alkali refers to a substance having 
a basic reaction. As applied to the soil, however, this restricted meaning 
does not hold, and alkali refers to any soluble salts that make the soil solution 
sufficiently concentrated to injure plants. This includes the chlorides, sul- 
phates, carbonates, and nitrates of sodium, potassium, and magnesium, and 
the chloride and nitrate of calcium. The sulphate and carbonate of calcium 
are not sufficiently soluble to be injurious to crops. Most of the alkalies are 
in reality neutral salts. It may be somewhat unfortunate to use for general 
substances a word that has become so well established in agricultural literature 
that it would now be very difficult to change it.” The author also emphasizes 
the great number of purely scientific problems connected with alkali soils and 
the need of much fundamental research in this field. 
The book includes 16 chapters: 1. Introduction; 2. Geographical dis- 
tribution; 3. Origin of alkali; 4. Nature of alkali injury to plant; 5. Toxic 
limits of alkali; 6. Native vegetation as an indicator of alkali; 7. Chemical 
methods of determining alkalis; 8. Chemical equilibrium and antagonism; 
9. Relation of alkali to physical conditions in the soil; 10. Relation of alkali 
to biological conditions in the soil; 11. Movement of soluble salts through the 
soil; 12. Methods of reclaiming alkali lands; 13. Practical drainage; 14. 
Crops for alkali land; 15. Alkali water for irrigation; 16. Judging alkali 
d.—Wwa. CRocKER. 
NOTES FOR STUDENTS 
Vegetation of Tasmanian mountains.—In reporting in some detail a 
study of the mountain vegetation of Tasmania, Miss Gress® sketches the 
position of the geological history of the island that most directly concerns its 
5 Harris, F, = Soil alkali, its origin, nature, and treatment. pp. xvi+258. 
Wiley & Scan 19 
° Grpss, L. :, bichon on the phytogeography nag tg of the mountain summit 
plateaux Hg Tasmania. Jour. Ecol. 8:1-17, 89-117. 
