ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. 85 



Action of the Amount of Heat and of Maximum Temperature on 

 the Opening of Flowers.* — W. von Vogel states, as the results of a 

 series of experiments, that the maximum temperature of the day has 

 seven times greater influence on the opening of flowers than the 

 average daily temperature. The mode of obtaining this result is 

 detailed in the paper. 



Behaviour of Vegetable Tissues towards Gases.f — J. Boehm 

 describes an apparatus which he has contrived for the purpose of 

 testing the variations, under different conditions, in the absorption of 

 gases by vegetable tissues, by starch, and by coal. One of the most 

 interesting of his conclusions is that the cell-wall is more permeable 

 for oxygen than for nitrogen. Dry filings of wood and of starch- 

 grains absorb four or five times their weight of carbonic acid, 

 while cork absorbs comparatively little. Carbonic acid, oxygen, and 

 hydrogen all become compressed in closed cells, owing to their greater 

 diflfusibility as compared to nitrogen. 



Influence of External Pressure on the Absorption of Water by 

 Roots.l — J. Vesque has carried out a series of experiments on this 

 subject, chiefly on two plants, one woody, the oleander, and the other 

 herbaceous, the garden bean. The following is a summary of the 

 results arrived at : — 



1. The absorption of water by the roots of the oleander depends on 

 external pressure ; it seems to augment in proportion to the difference 

 between the external pressure and that of the air contained in the 

 woody mass of the root. 



2. Osmose does not appear to be always very active ; for, in 

 diminishing the atmospheric pressure to about 60 cm. of water, 

 absorption is arrested. 



3. In the conditions of the experiments the pressure of the internal 

 air is not very different from that of the atmosphere. It is mostly 

 less from zero to 9 cm. of mercury ; in one instance only did the 

 internal pressure exceed that of the atmosphere by 1 cm. of mercury. 



4. The effect of pressure on the oleander is sufficient for a sudden 

 change of barometric pressure to cause a sensible disturbance in the 

 absorption of water by the roots. 



6. The garden bean was much less influenced by external pressure, 

 as respects the absorption of water by the roots, than the oleander. 

 There certainly is some influence, but it is ordinarily imperceptible 

 among fluctuations resulting from changes of transpiration or from 

 other secondary causes. 



Contrivances for the Erect Habit of Plants, and Influences of 

 Transpiration on the Absorption of Water.§ — V. Meschayeff does not 

 agree with Schwendener's view that there is a special tissue-system for 

 the purpose of maintaining organs in an erect condition ; he considers, 



* Bull. Soc. Imp. Nat. Moscou, Iviii. (1883) pp. 1-13. See Bot. Centralbl., 

 xvi. (1883) p. 145. 



t Bot. Ztg., sli. (1883) pp. 521-6, 537-50, 553-9. 



j Comptes Eendus, xcvii. (1883) pp. 718-20. 



§ Bull. Soc. Imp. Nat. Moscou, 1883, pp. 299-322. 



