NOTES ON RECENT RESEARCH. 



1107 



whereas these under a reduced pressure remained paler in colour, and 

 several amongst them remained completely etiolated. 



On February 21 three other lots were experimented upon ; lot 1 

 under normal pressure ; lot 2 half an atmosphere ; and lot 3, one 

 sixth of an atmosphere. On March 1, lots 1 and 2 were green, the 

 latter the paler of the two, whereas lot 3 remained completely 

 etiolated. 



In a second series of experiments, oxygen alone was used, the pressure 

 being about half an atmosphere. Under these conditions the plants 

 became as green as those growing in the open air. 



Experiments with Phaseolus multiflorus corroborated all the above 

 results. These plants under a pressure of one sixth of an atmosphere of 

 atmospheric air remained etiolated, whereas under an equal pressure of 

 oxygen the green colour was equal to that of plants growing in the 

 open. 



A further experiment with plants hermetically sealed in a globe, 

 furnished with an arrangement for absorbing the carbonic acid given off 

 by the plants, enabled the author to formulate the following : 



In rarefied air the formation of chlorophyll is much diminished. It 

 is the insufficiency of oxygen, and not the accumulation of carbonic acid 

 gas, that retards the formation of chlorophyll. — G. M. 



Daphnine. 



Daphnine, Localisation of, in Daphne Laureola. By M. W. 



Eussell (Rev. Gen. Bot. t. xiv., 1902, p. 420).— The Daphne Laureola is 

 known to possess poisonous properties, and the cortex of the stem, which 

 is the officinal portion, contains the substance daphnine, though it is not 

 certain whether it is to this body or to the resinous or oily secretion that 

 the plant owes its utility. The daphnine is a glucoside, and can be 

 detected by adding to tissues containing it a solution of iodide of potash. 

 This gives rise to a rose colour passing through orange, carmine, and 

 finally to reddish-brown. Various other tests are also given. The 

 daphnine is shown to be localised in the bundles and in the epidermis 

 as far as the leaf is concerned. In the stem the glucoside is localised in 

 the epidermis, phelloderm, bast, parenchyma, and medullary rays. It 

 occurs also in the root (sparingly) and in the flowers. — /. B. F. 



Plankton Diatoms. 



Diatoms of the Plankton, Statistics of Varieties in. By 



Schroter & Vogler {Flora, xci. 1902, pp. 380-383).— This is an abstract by 

 P. Vogler of (1) a research published by him in the Vicrtelj. Naturf. Ges. 

 Zur. vol. xlvi. 1901. Every month the width of 100 ribbons of Fragil- 

 laria were measured so as to give the length of the single frustules ; 

 (2) another by Schroter's pupil, Lozerau, on Asterionclla gracillima and 

 Tabellaria fenestra. The chief result is that in the Plankton Diatoms 

 auxospore-formation occurs after long intervals of vegetative reproduction. 

 During these the size of the individuals gradually diminishes. The 

 conditions of auxospore-formation have still to be determined. — Jl. H. 



