680 SUMMAEY OF CUREENT EESEAECHES EELATING TO 



exerted on the plant from witliout, no diffusion takes place. When 

 the consumption of water is greater than the supply, bubbles, not of 

 air, but of aqueous vapour, arise so soon as the conducting elements 

 are protected from the access of the external air. The bubbles which 

 make their appearance in microscopic sections can only be air-bubbles 

 when the making of the section does not prevent the access of the 

 external air. Even with the water of transpiration no air can reach 

 the woody elements in which this takes place. The escape of bubbles 

 of gas from " weeping " rootstocks and other parts of plants, and the 

 mixture of bubbles of aqueous vapour with those of air, can be ex- 

 plained by the access of the external air on making the section, and to 

 the opening of cells or vessels which are filled with aqueous vapour 

 and impermeable to air when closed. The observations of the author 

 confirm the statement that no bubbles of air occur in the conducting 

 organs of growing plants. 



Ammoniacal Ferment.* — According to M. A. Ladureau, the 

 ferment which transforms urea into ammonium carbonate occurs in 

 the soil, the air, water, rain, &c. It acts in vacuo as under normal 

 pressure, also under the pressure of three atmospheres, and in the 

 presence of oxygen, hydrogen, nitrogen, carbon, &c. Antiseptics act 

 on this ferment only when present in large quantities ; of anaesthetics 

 chloroform only modifies its action. 



Source of the Nitrogen of the Leguminosse.f — M. B. E. Dietzell 



has grown clover and peas under conditions as nearly natural aS 

 possible, in pots of ordinary garden soil, in the open air, but sheltered 

 from the weather and watered with pure distilled water. The quantity 

 of nitrogen in the soil, the seeds, and the mature plant was deter- 

 mined, and the result arrived at was that peas and clover do not absorb 

 combined nitrogen from the air. In all cases except two there was 

 an actual loss from 5*1 to 15 • 32 per cent, of the nitrogen in the soil. 



Absorption of Atmospheric Nitrogen by Plants.J — Mr. W. O. 

 Atwater describes a series of experiments in growing peas in a nutrient 

 fluid composed of potassium nitrate, calcium nitrate, calcium phos- 

 phate, magnesium sulphate, and chloride of iron, and protected from 

 rain and dew. He finds as a uniform result that the mature plant 

 contains much more nitrogen than it could have obtained from the 

 nutrient fluid and from the store of food-material in the seed. The 

 amount of nitrogen thus obtained from the atmosphere increased in 

 proportion to the supply of nutrient material in the root. In some 

 of the experiments from one-third to one-half of the total amount of 

 nitrogen in the plant must have been obtained in this way. 



The author is unable to determine in what form and through 

 what organ this nitrogen was absorbed by the plant, whether as free 

 nitrogen, or as ammonia, nitric acid, or any other compound, and 



* Comptes Eendus, xcix. (1884) p. 877. 



t Ann. Agronomiques, x. pp. 513-4. See Journ. Ohem. Soc. — Abstr., xlviii. 

 (1885) p. 418. 



% Amer. Ohem. Journ., vi. (1885) p. 365. See Naturforscher, xviii. (1885) 

 p. 237. 



