222 EXPERIMENT STATION RECORD. 



consists essentially in placing upon the under surface of the leaf a small portion 

 of a certain liquid and observing the rate of its infiltration as evidenced by 

 its ^forming in that part of the leaf a spot which, by transmitted light, is 

 translucent. 



For this purpose it is stated that water will not answer, but alcohol is found 

 suitable, while benzol, xylol, and oil of turpentine are very much more sensitive 

 indicators in most cases. With a decrease of the openings, filtration diminishes. 

 At a certain point alcohol, it is claimed, ceases to pass, while the other liquids 

 continue to enter, thus distinguishing between very small degrees of opening 

 and absolute closure. Detailed and tabulated findings are given of a great 

 number of studies carried on with many different plants. Stomata in fresh 

 leaves were nearly always found to be open on sunny days, but nearly or en- 

 tirely closed at night. In case of wilted and dried leaves the stomata were 

 usually almost or quite closed, in many cases even to benzol. 



Several advantages are claimed for this method over others now in use, some 

 of which are here discussed, as are also the results obtained by their employ- 

 ment. 



A new method of estimating' the aperture of stomata, F. Darwin and D. F. 

 M. Pertz {Proc. Roij. Boc. [London], Ser. B, 8-J (Wll), Xo. B 569, pp. 136-15Ji, 

 figs. 10; ahs. in Ztschr. Bat, 4 {1912), No. 2, pp. 1^2, i-^S).— The estimate of 

 stomatal aperture obtained by this method (called the porometer method) 

 is based upon the amount of air drawn through a funnel tube, glued to 

 the stomatal surface of the leaf, as shown by a column of water in the 

 stem of an attached and partly exhausted T-tube. The air is drawn through 

 the stomata outside the glass funnel, through the leaf tissue, and again through 

 the stomata inside, its amount and variations being measured by means of the 

 fall of the water column in the stem of the T-tube. The merits claimed for 

 the method are that (1) the results obtained are independent of transpiration 

 and (2) the living, uninjured stomata can be studied continuously for hours 

 or days together. 



Among the results given of studies already made by this method, it is 

 claimed to have been shown that in case of leaves severed from the plant the 

 first effect of withering is the opening of the stomata, followed, however, by 

 their closure. Publication of other results is also promised. 



Transpiration in wet leaves, V. S. Ilin {Trudy Imp. S. Peterh. Obshch. 

 Estestvo. {Trav. Soc. Imp. Xat. St. Pet^sb.), J,2 {1911), III, No. 2-8, pp. 359- 

 414, figs. 23). — This is an account of a series of experiments on the transpira- 

 tion and related phenomena in leaves soaked in water or in solutions of salts. 

 It was found that when the stomata are open naturally transpiration in wet 

 plants is always heightened and that such plants desiccate rapidly, the curve 

 of transpiration approximating that shown by plants in the damp atmosphere 

 of dewy mornings. If compelled to open their stomata, however, by immersion 

 in potassium nitrate solution, the plants show no increase in transpiration or 

 in rapidity of desiccation. No such increase of transpiration follows the wetting 

 of plants the stomata of which are closed, except a slight increase observable 

 after long immersion in case of plants having thin cuticle. Immersion tends 

 to cause closure of the stomata, but this tendency is opposed by light. Some 

 leaves lost up to 43 per cent of their weight before their stomata were found 

 to be closed. Transpiration curves showed interrupted variations which bear 

 a certain relation to the curves of water absorption by the leaves. 



Transpiration and the ascent of sap, H. H. Dixon {Ann. Rpt. Smithsn. Inst. 

 1910, pp. Jf07-Ji25. figs. //). — A summary is given of evidence that is held to 

 support the author's cohesion theory of the ascent of sap in plants (E. S. R., 18, 

 p. 825; 21, p. 725). 



