GIVEN OFF BY PLANTS DUEING THEIR GROWTH. 



39 



types of the agricultural plants of the Leguminous family, have 

 also been the subjects of experiment for several years past, and we 

 hope before long to complete the results for publication. 



Besides the experiments of a more purely agricultural scale and 

 character, however, it was thought that the explanation of the 

 alternation of crops would materially be aided by any additional 

 information as to the characteristic qualitative and quantitative 

 functional actions of some of the plants which ordinarily find a 

 place in rotation. With this view it was sought to ascertain, as 

 in some degree a measure of the activity of the processes of the 

 plants, the amount of water passed through those belonging to 

 different natural orders, and holding different positions in rota- 

 tion, both as compared one with another, and in reference to the 

 quantitative fixation in the plants, of several of their more im- 

 portant constituents, having regard also, as far as was practi- 

 cable, to the source of these constituents — that is to say, as to 

 whether they were derived from the soil or from the atmosphere. 



The experiments, as thus far proceeded with, however, can be 

 considered as little more than initiative, especially so far as the 

 demonstration of those important agricultural problems, for the 

 elucidation of which they have mainly been designed, is con- 

 cerned : were it otherwise, indeed, the pages of this Journal 

 would not be deemed the fittest medium for the publication of 

 results of more purely agricultural interest. The facts already 

 obtained, however, are not without interest to the botanist and 

 the vegetable physiologist ; and it is as a contribution to the 

 scanty information already at command on the subject of the 

 amount of water given off during the growth of plants, that these 

 results are arranged and presented to the reader. It will never- 

 theless be seen, that they provide some important and interesting 

 indications in reference to the more special object of our investi- 

 gation, and at the same time afford some useful suggestions for 

 its future conduct. 



In deciding upon the method of procedure, the choice seemed 

 to be between such experiments as would yield somewhat rapid, 

 and in some points, perhaps, more direct information, though at 

 the cost of the health and perhaps matured growth of the plant, 

 on the one hand, and a closer imitation of the usual circumstances 

 of growth on the other — by which, however, inferences rather 

 than demonstration might be elicited. The latter course was 

 chosen, more especially as there are well-conducted experiments 

 of the former kind on record, which it was thought might serve 

 to check or confirm some conclusions which our own results, 

 taken alone, might be held not fully to justify. 



It was considered important to provide such conditions for the 

 plants as should enable them to live and mature their seed, if 



