562 SCIENCE PROGRESS 



investigated, and Yuncker (Plant World, 19, 1 51-61, 1916) 

 has determined its influence on transpiration in the corn plant. 

 He found that the " water requirement " (the quantity of water 

 transpired per unit production of dry matter) of his plants was 

 greater in a moist soil than in a dry one. Iljin (Journ. Ecol. 4, 

 65-82, 19 1 6) working on slightly different lines has obtained 

 exactly similar results. Experimenting on rather dry ground 

 in the open, he found that a drought-resisting capacity in a 

 plant is accompanied by a correspondingly low transpiration 

 rate, relative to the amount of assimilation taking place. Bow- 

 man (Proc. Nat. Acad. Sci. U.S. A. 2, 585-8, 1916), working with 

 mangrove seedlings, found a greater transpiration rate resulting 

 from an increased concentration of the sea water with which 

 he watered his (sand) cultures. These results appear to resolve 

 themselves into a question of the reduction of concentration of 

 nutrient substances, in the one case by addition of water, and 

 in the other of salt, but further speculation is liable to prove 

 unprofitable. The question arises from Iljin's results, whether 

 the capacity of some types to employ the water supply to 

 greater advantage than others might be applied to the cropping 

 of semi-arid regions. 



Livingston (Johns Hopkins Univ. Circular, 191 7, 176-82) 

 finds from water culture experiments that a plant may go 

 through all stages of water loss from incipient drying to tem- 

 porary, and finally, permanent wilting without any reduction 

 in the power of the surrounding medium to supply water to the 

 roots. He therefore concludes that reduction of water content 

 may occur as the result of purely internal factors. 



The comprehensive work of Dixon and Joly has caused some 

 attention to be directed to a physiological study of the wood 

 of stems, with a view to obtaining knowledge of the passage of 

 water. Bailey (Bot. Gaz. 62, 133-42, 191 6) finds the bordered- 

 pit closing membrane of conifers to be perforated and readily 

 permeable to gases and liquids. Nordhausen (Jahrb. j. wiss. 

 Bot. 58, 295-335, 191 7) finds the problem of the ascent of sap 

 no nearer solution owing to various difficulties, including 

 interference with the continuity of the water columns by air 

 bubbles, and the impossibility even at great tensions of drawing 

 through a stem sufficient water to cover the losses by transpira- 

 tion. Work in this direction appears continually to marshal 

 more facts than can be explained by the simple cohesion and 



