1916] AGRlCULTUKAL BOTANY. 431 



/hmts, by F. M. Andrews; Thiospirillum jenense and its Reaction to Liglit Stim- 

 ulus, by J. Buder; Spore Generation and Release by Coprimis sterquilinus, by 

 A. H. R. BuUer ; The Distribution of Certain Liverworts of tli6 Malay Region, 

 by D. H. Campbell ; Physiological Fragments from a Tropical Forest, by F. C. 

 von Faber ; Anatomical and Physiological Studies on the Flowers of the Orchid 

 Genera Catasetum and Cycnoches, by H. R. von Guttenberg; Gas Exchange in 

 the Marine Algae, by R. Harder; Disorganization of the Tapetum Cells in 

 Pollen Sacs of Angiosperms, by H. O. Juel ; Growth and Rest of Tropical 

 Trees, by G. Klebs ; Nutritive Physiology of Extreme Atmospheric Epipliytes, 

 by R. Lieske ; Problems Regarding the Twining of Plants, by H. Miehe ; Studies 

 on Prothallia of Ferns with Regard to Imbedded Antheridia and Apogamy, by 

 D. M. Mottier; The Behavior of Twining Plants in Darkness, by F. C. New- 

 combe ; A Multiple Clinostat, by G. Peirce ; and Laws Regarding the Compensa- 

 tion Relations of Parallel and Opposed Light and Mass Impulse, by A. Sperlich. 



A convenient modification of the porometer, R. C. Knight (New Phytol., 1^ 

 {1915), No. 6-7, pp. 212-216, fig. i).— The author describes a form of porometer 

 which he has devised, w^ith a typical experiment illustrating its use. Some 

 advantages are claimed for this form over that used by Darwin and Pertz 

 (E. S. R., 27, p. 222). 



On the use of the porometer in stomatal investigation, R. C. Knight (Ann. 

 Bot. [London], 30 (1916), No. Ill, pp. 51-16, figs. 7).— This is an account of 

 preliminary experiments carried out looking to discovery of possible sources of 

 error in work done with the porometer above mentioned. These include tem- 

 porary deformations of the leaf due to pressure differences, the tendency of 

 stomata to close when air is drawn continuously through them, the temporary 

 tendency to close after rough handling, and the disproportionately great resist- 

 ance offered by intercellular spaces. In the plants investigated there was a 

 considerable similarity in the behavior of the stomata of different leaves, but 

 still more in that of those of the same leaf. Stomata of a mature healthy leaf 

 may open more widely than those of either a very young or very old leaf. 



A description of a recording porometer and a note on stomatal behavior 

 during wilting, C. G. P. Laidlaw and R. C. Knight (Ann. Bot [London'], 30 

 (1916), No. Ill, pp. 41-56, figs. 3). — The apparatus here described is essentially 

 a continuously acting, self-recording modification of the porometer briefly de- 

 scribed in the paper noted above. A constant-pressure aspirator is employed to 

 draw air through the leaf, and the speed of the air stream (infereutially also 

 the relative size of the stomatal apertures) is measured by the rate of flow. 

 The results obtained are said to be very satisfactory, and to show close agree- 

 ment with the observation of Darwin and Pertz that in case of a leaf detached 

 from the plant the stomata opened temporarily before their final closure, the 

 phenomenon being ascribed to wilting. 



The gas exchanges of water plants, H. Kniep (Jahrb. Wiss. Bot. [Prings- 

 heim], 56 (1915). Pfeffer-Festchr., pp. 460-510). — This is a contribution on the 

 method of bubble counting, and the several sections deal with the oxygen con- 

 tent of the bubbles as related to the rapidity of their formation, the effect of 

 water movement on bubble production, the interruption of bubble production 

 by interruptions of the light supply, and a new method of ascertaining the 

 minimum light intensity required for assimilation. 



Synthetic processes in plants, II, P. Boysen-Jensen (Jahrb. Wiss. Bot. 

 [Pringsheim], 56 (1915), Pfetfer-Festschr., pp. 431-446). — Continuing earlier 

 work (E. S. R., 28, p. 127), the experiments described are claimed to have 

 shown that two stages may be distinguished in the germination of peas. In the 

 first of these cane sugar is utilized, partly for growth, partly for respiration. 

 Separated cotyledons show a decrease of cane sugaj-. In the second stage the 



