530 EXPERIMENT STATION RECORD. 



Evidences of adaptation to conditions of exposure to very dry air and to the 

 hot sun are noted. The adaptive devices mostly fall into 2 general categories, 

 one of elements contributing to the accumulation of water, as storing spaces 

 and tissues generally, and the second of elements retarding loss, as reducetl 

 evaporative surfaces, thickness of cuticle, scarcity of stomata, gelatinous cell 

 contents, etc. 



A brief bibliography is appended. 



The water relations of desert plants, D. T. MacDougal (Poj). Sci. Mo., 7.9 

 (1911), No. 6, PI). SJfOSSS, figs. 5). — This is a popular presentation, in part of 

 matter previously noted (E. S. R., 25, p. 219). After some general discussion 

 of desert types nwd. of their behavior under natural or controlled desiccation, 

 the results of further investigations are given. 



It vpas found that the transpiration of a leaf increases from early morning 

 until some time in the forenoon, vphen it suddenly drops. An explanation 

 offered is that the film of moisture on the internal leaf cells thins out and 

 breaks, and that thereafter evaporation can take place only from the edges of 

 the water layers in the interstices. This breaking point shows no regular rela- 

 tion to the wilting point of a plant. 



A discovery was also made that there is a large daily variation in the acidity 

 of the succulents, the amount of acid present at the maximum in the morning 

 being frequently about 4 times that found at the minimum in the evening. 

 The change seems to be related to the course of the temperature, and it may 

 be significant in connection with the water-holding capacity of the cell colloids. 



Concerning the value of the great water balances of the succulent plants, a 

 review of the extensive data accumulated establishes the fact that Echinocactus 

 may live for nearly 3 years at the expense of its water balance, which may be 

 depleted as much as 50 per cent before death results. Carnegiea loses nearly 

 30 per cent before serious results follow, and its seedlings may live when re- 

 duced to only one-third of the original weight. 



The role of individual nutritive elements in the activity of the plant, 

 A. G. DoiAKENKo (Dnevn. XII. S"iezda Russ. Est.-Isp. i Vrach [Moscow], p. 

 673; aljs. in Zhur. Opytn. Agron. (Russ. Jour. Expt. Landiv.), 11 {1910), No. Jf, 

 pp. 600, 601). — Experiments were conducted to determine the influence of a 

 deficiency or excess of nitrogen, phosphoric acid, and potash on the total yield, 

 the relative yield of the different plant organs, and the accumulation of various 

 organic substances in plants. 



The data obtained seem to indicate that the nitrogenous materials influence 

 the predominance of leaf organs, and potash the predominance of the stem 

 organs. Potash, in the case of flax, increased the amount of fiber. 



A detailed study of the formation of various nitrogenous compounds seems to 

 show that under the infiuence of potash nutrition nonalbuminoid nitrogen is 

 accumulated as well as organic bases and amids. 



The role of silica in the nutrition of plants, A. Sprecher (Bui. Soc. Bot. 

 Oenivc, 2. set:, 3 {1911), No. //, pp. 155-192, figs. 4). — Experiments with Avena 

 steriUs grown in 4 culture solutions with and without silica are reported. 



The Knop-Pfefter solution gave the best results. This is believed to be due 

 to the slight acidity from the iron chlorid and potassium acid phosphate. The 

 addition of silica to the solutions in general increased the dry weight as well 

 as the important constituents, such as ash, proteid substance, crude fiber, and 

 carbohydrates, although there was some variation in the proportion, due prob- 

 ably to the different culture solutions. 



"Where the same compounds were available silica was less abundant in the 

 well grown plants than in those poorly develoi>ed. The percentage of mineral 

 salts absorbed by the plants diminished with the addition of silica, although 



