250 PHYSIOLOGY [Bot. Absts. 



1740. Weber, Friedl. Die Plasmaviskositat pflanzlicher Zellen. [Review of recent work 

 on the viscosity of the protoplasm of plant cells.] Zeitschr. Allg. Physiol. (Referate) 18 1 : 1-20. 

 1918. — Two methods of determining the viscosity of protoplasm are described. The viscosity 

 of the protoplasm of the starch-sheath cells of Viciafaba is 23 times that of pure water. The 

 viscosity decreases with rising temperature, the temperature coefficient being the same as 

 for albumen, lying between 1.51 and 1.27. At extremely high temperatures a decided increase 

 in viscosity occurs ("Warmestarre"). One to 5 per cent ether decreases the viscosity ; 5 to 

 10 per cent increases it. Small amounts of aluminium salts markedly increase the viscosity. 

 Long immersion of sections in water decreases the viscosity, which rises near the time of 

 death. Wounding increases the viscosity. Mechanical shaking decreases the viscosity, 

 stronger or longer continued shaking increases it. A discussion of the relation of the influ- 

 ence of gravity on viscosity and geoperception is given. — William J. Robbins. 



WATER RELATIONS 



1741. Sayre, J. D. Comparative transpiration of tobacco and mullein. Ohio Jour. Sci. 

 19: 422-426. 1919.— In this preliminary paper the following conclusions are given: Mullein 

 leaves offer greater resistance to water-loss in darkness than in light, and less in wind than in 

 still air. They are as responsive to environmental changes as tobacco leaves. The removal 

 of the hairs from mullein leaves affects cuticular transpiration only. In the course of a day, 

 water-loss is first accelerated by the increased diffusion gradient through the opened stomata. 

 At midday this becomes counterbalanced by leaf-water deficit and decreasing stomatal pores. 

 Eventually the diffusion gradient decreases and the night rate is reached before the stomata 

 are fully closed. Autonomic transpirational rhythm was observed in certain cases when plants 

 were left in darkness for a day. The conditions controlling this rhythm are described. [See 

 also next following Entry, 1742.] — H. D. Hooker, Jr. 



1742. Sayre, J. D. Factors controlling variations in the rate of transpiration. Ohio Jour. 

 Sci. 19: 491-509. Fig. 1-9. 1919.— Experiments to determine the factors controlling trans- 

 piration and its rhythm in darkness in Verbascum thapsus and Nicotiana sp. are described. 

 Temperature and humidity were recorded by a hygrothermograph, checked by a psychrometer. 

 Evaporation rates were determined by porous-cup atmometers. Transeau's automatically 

 recording apparatus was used to determine rates of water-loss from the plants. The size of 

 the stomatal pores was measured by Lloyd's method, after fixation in absolute alcohol. 

 Transpiration at night is entirely cuticular. The day rate is controlled by the following fac- 

 tors: stomata, leaf -water deficit, and diffusion gradient. These factors combine to give a 

 rounded curve. Tobacco and mullein show a rhythm in the transpiration curve in total dark- 

 ness on a day following normal light conditions. This is absent on the second day, and was 

 not found on the first day in Verbascum blattaria. The cause of the rhythm is thought to be 

 stomatal activity. [See also next preceding Entry. 1741.] — H. D. Hooker, Jr. 



MINERAL NUTRIENTS 



1743. Miller, H. G. Relation of sulphates to plant growth and composition. Jour. 

 Agric. Res. 17: 87-102. PL 9-12. 1919.— See Bot. Absts. 3, Entry 1770. 



PHOTOSYNTHESIS 



1744. Spoehr, H. A. The carbohydrate economy of cacti. Carnegie Inst. Washington 

 [D. C] Publ. 287. 79 p., fig. 1-2. 1919.— Sugars are the first products that accumulate in the 

 process of photosynthesis of carbon compounds and are considered the starting point for the 

 synthesis of other compounds in all living matter. The tissues of cacti behave like masses 

 of gels composed largely ( f colloidal carbohydrates among which are large quantities of pen- 

 tosans. Organic compounds c< ntaining hydroxy! groups (o. g., carbohydrates) are very weak 

 acids and while the sugars are stable substances, their salts decompose very readily, resulting 



