H. BOTANY AND HORTICULTURE. 289 



that a yield of even 2^ to 3 per cent, of nitrogen from the 

 dry leaves is not common. 14 C, C, 326. 



POISON FR03I THE SHADE OF THE MANZANILLA. 



Mr. Karsten has published the detail of observations made 

 upon himself in reference to poison by exposure to the shade 

 of the manzanilla-tree (Hippomanes manzanilla.) After re- 

 maining several hours under the tree, he experienced a burn- 

 ing sensation over the entire surface of his body, which at 

 length centred in certain parts of the skin, especially about 

 the face, and above all around the eyes. After a time the 

 eyes were swelled so as to be almost closed, and were so sen- 

 sitive that for several days he found it necessary to remain* 

 in a perfectly-darkened room, being also in great pain. After 

 three days the swelling diminished, and the epidermis began 

 to peel off. These symptoms he supposed to be the result of 

 poisonous exhalations from the tree, a peculiarity which is 

 shared with the manzanilla in South America by several oth- 

 er species of plants. An analogue of these deleterious exha- 

 lations may be seen in certain volatile organic bases, such as 

 trimethylamin ; and it is suggested that similar nitrogenous 

 combinations may have a much w^ider distribution than has 

 hitherto been suspected. 18 C, 1871, July 19, 453. 



TRANSPIRATION OF LEAVES. 



Von Pettenkofer, in the course of his researches upon the 

 amount of evaporation which takes place from the foliage of 

 plants, ascertained in the case of an oak-tree that this in- 

 creased gradually from May to July, and then decreased till 

 October. The number of leaves on the tree were estimated 

 at about 751,600, and the total amount of evaporation in the 

 year at 539 cubic centimetres of water for the whole area of 

 the leaves. As the average rain-fall for the same period was 

 only 65 centimetres, the amount of evaporation is thus eight 

 and a half times greater than that of the rain-fall. This ex- 

 cess must, of course, be drawn up by the roots from a great 

 depth. The inference is derived from the above that trees 

 prevent the gradual drying of a climate by restoring to the 

 air the moisture which would otherwise be carried off by 

 drainage. 13 A, February 1, 120. 



N 



