AGRICULTURAL BOTANY. 527 



suited to the supposedly trying climate to which the plants studied by the 

 author are subject. As long as a water supply is available and the plant is 

 kept cool by transpiration, it suffers no more in the Tropics than in temperate 

 regions. There does not seem to be any evidence that the behavior of the 

 stomaia tends to mollify the rigor of the environment. 



A bibliography of the subject is given. 



The influence of a mixture of soluble salts, principally sodium chlorid, 

 upon the leaf structure and transpiration of wheat, oats, and barley, L. L. 

 Haeter (C7. »s'. Dcpt. Agr., Bio: Phint Indus. Bui. IS.',, pp. 22). — The investi- 

 gation reported was undertaken with a view of ascertaining whether the 

 presence of a mixture of soluble salts, consisting chiefly of sodium chlorid, such 

 as occurs in excessive quantities in many alkali soils, will affect the structure 

 of ])lants not especially adapted to such soils, and if modifications of structure 

 take' place whether they resemble those which characterize plants growing 

 naturally in saline soils. 



It was possible to demonstrate that cultui-e in a soil containing considerable 

 quantities of sodium chlorid together with other salts produces measurable 

 changes in the leaf structure of wheat, oats, and barley. The most notable 

 modification produced was the conspicuous bloom or waxy deposit that formed 

 on the surface of the leaves. This development of bloom was accompanied by 

 an easily measured increase in the thickness of the cuticle and outer walls of 

 the epidermal cells and by a marked decrease in their size. 



In regard to transpiration of the ])lants, it was found that when the alkali 

 salts ai"e present in sufficient concentration to cause the modifications of struc- 

 ture noted, transpiration is considerably reduced. On the other hand, the same 

 salts when present in amounts too small to produce any measurable influence 

 upon structure have a decidedly stimulating effect upon transpiration. 



The value of sodium to plants by reason of its protective action, W. J. V. 

 OSTERHOUT {Univ. Cal. Pubs., Bot., 3 (1908), Ko. 3, pp. 331-337). — According 

 to the author, the idea that sodium is valueless to plants is based on the nutri- 

 tive function of mineral salts and does not take into considei-atiou their pro- 

 tective function. In previous publications (E. S. E., 19, pp. 727, 933), the 

 author has confirmed Loeb's conception regarding balanced solutions when ap- 

 plied to plants. 



Experiments with sodium v. potassium, ammonium, magnesium, and calcium 

 in water cultures and in sand showed with a large number of plants a pro- 

 tective influence against the injury resulting from growing plants in cultures 

 to which a single salt solution was added. 



It seems clear that sodium has no nutritive function in plants, but only a 

 protective action, and this seems to be also the case for animals. It appears 

 probalile that sodium may render the plant a useful service as a protective 

 agent, and in the case of certain plants it appears to be indispensable. 



The protective effect of sodium on plants, W. J. V. Osterhout (Jahrb. 

 Wiss. Bot. [Pringshcim], 46 (1908), No, 2, pp. 121-136, figs. 3).— This is a de- 

 tailed account of the experiments noted above. 



Notes on hydrocyanic acid in some plants, A. W. K. de Jong (Ann. Jnrd, 

 Bot. Buiicnzorg, 2. so:, 7 (1908), pt. 1, pp. 1-11, flg. i).— The author has made 

 an investigation of the hydi'ocyanic acid contained in Pangium cdule, and finds 

 that the glucosid occurring in the leaves of that plant is identical with gyno- 

 cardine, a glucosid occurring on the seeds of flynocardia odorata. 



A study was made of the presence of free liydrocyanic acid in the leaves of 

 Pangium, and the author found that it is formed in greater or less quantity. 



