430 EXPERIMENT STATION RECORD. 



The book treats of pltint physiology with si)ocial reference to plant production. 

 It does not pretend to treat exhaustively any topic but offers a wide range of 

 material showing plant behavior under all conditions. As such it should be of 

 value in agricultural, horticultural, and other classes where a knowledge of 

 plant activity is of high importance as a part of the training for practical and 

 rural life. The different chapters are followed by series of suggestive labora- 

 tory exercises for students by which the principles described are clearly demon- 

 strated. References to special articles are freely given, and numerous text- 

 books are cited for fuller discussions of the principles involved. A feature of 

 the work is the frequent use of illustrative material from plants that are 

 familiar and directly useful rather than the standard illustrations drawn from 

 rare and often unattainable material. 



The plant cell, H. A. Haig {London, 1910, pp. IX+201, table 1, pis. 12, figs. 

 112). — The text deals with the study of structural and physiological botany from 

 a biological standpoint. The working substance of a cell, the protoplasm, is 

 given first place in importance, and the subsequent changes in form, function, 

 etc., are looked upon as being due to the protoplasm under the stimulus of 

 various physical and chemical forces. 



Studies on the influence of low temperatures on plant cells, E, Schaffnit 

 (Ztschr. AU(j. Physiol., 12 {1911), No. 3, pp. 323-336). —Previously noted from 

 another source (E. S. R., 24, p. 533). 



The water supply and the osmotic pressure conditions of desert plants, 

 H. Fitting {Ztschr. Bot., 3 {1911), No. J,, pp. 209-275).— This is an extended 

 investigation of the means by which desert plants obtain their water, special 

 attention being given to the water-absorbing power of certain desert species as 

 indicated by their intensified osmotic pressure. 



The results are given of tests of the osmotic pressure of plants of stony 

 deserts, of extremely dry, rocky deserts, of desert plants when grown in damp 

 soils, of plants growing on very saline, wet soils, of dune plants, and of some 

 plants from the Desert of Oued Biskra. 



It is claimed that neither annual nor perennial plants in the Sahara Desert 

 replenish their loss of water from dew, as there is no dew in this region, and 

 also that only to a limited extent can most of the perennial desert plants draw 

 on the very deep ground water, because the soil conditions for many of the 

 common kinds of plants are such as to make it impossible for their roots to 

 penetrate to any great depth. Careful studies of the vegetative conditions of 

 desert plants force the conclusion that in such dry deserts as the Sahara the 

 water supply of perennials which have no storage tissues must come from the 

 upper dry-soil layers. It is also stated that in very dry years the nonxero- 

 phytic annuals obtain their water supply from the uppermost dry-soil layers. 



From the author's observations and investigations it seems probable that 

 perennial desert plants have developed distinct adaptations and devices to 

 draw from the very dry soil the necessary moisture for plant growth. Such 

 adaptation would be the development of a very high osmotic pressure by which 

 means the plant would be enabled to absorb water from even the dry soil. It 

 was found that the osmotic pressure of many of the desert plants (a list of 

 which is given, together with their osmotic pressures) was very high, and 

 varied materially for the difl'erent species tested. 



Of the 46 species investigated, 21 per cent had an osmotic power of 3 gm. 

 of potassium nitrate, which is equivalent to a pressure of 100 atmospheres, 35 

 per cent had a pressure greater than 1.5 gm. (53 atmospheres), 52 per cent had 

 a pressure higher than 1 gm., and only 11 per cent had an osmotic pressure as 

 low as 0.3 to 0.6 gm. The lowest pressures were found in the annuals, and the 

 highest in the shrubs. Of the 10 species with a pressure of 3 gm. or more, 6 



