J. H. Gilbert— Points in connection with Vegetation. 101 



result is an annual yield of 55 - 2 lbs. of nitrogen over the first 

 ten years; of even slightly more, or fifty-six lbs., over the 

 second ten years: and of 55-6 lbs. over the whole period of 

 twenty years — that is, considerably more than twice as much 

 as would be yielded by a gramineous crop grown separately 

 on arable land. It may here be observed that, while in the 

 case of the first three plots referred to, the produce of the 

 mixed herbage diminished over the second as compared with 

 the first ten years, that of plot 7, with the potass manure, and 

 so much leguminous herbage, increased slightly over the sec- 

 ond compared with the first ten years. Finally, it may be 

 remarked on this point, how comparatively uniform is the 

 average yield of produce by all other species other than the 

 gramineous and the leguminous on the four very differently 

 manured plots. 



Here again, then, the results relating to the growth of species 

 of many different natural orders growing together, like those 

 relating to the growth of individual species grown separately, 

 show that those of the leguminous family, and probably those 

 of various other orders also, have the capacity of as- 

 much more nitrogen over a given area than species of the order 



Assuming for the sake of argument that the yield of nitrogen 

 by the Gramineas grown separately may be explained, as already 

 suggested, by reference to the amount of combined nitrogen 

 acquired from the measured aqueous deposits from the atmo- 

 sphere, together with that condensed within the pores of the 

 soil, and that derived from previous accumulations within it, 

 the question arises, can the gres i by other 



plants be so accounted for? or, if not, how otherwise may it 

 be explained ? We will endeavor to weigh the evidence bear- 

 ing upon this point. 



Is the combined nitrogen in the atmosphere the source of the asaim- 

 ilated nitrogen ? — It so happens that the plants which do gather, 

 or which have been supposed to gather nitrogen more readily 

 than the Graminese, have obviously a different character of 

 foliage; as, for instance, the "root crops"— turnips and the 

 like; and the leguminous crops — beans, pets, clover, etc. An 

 obvious explanation, therefore, which will be found in books 

 of authority, is that these so distinguished "broad leaved 

 plants" have the power of taking up nitrogen in some form 

 from the atmosphere, in a degree, or in a manner, not possessed 

 by the narrow-leaved gramineous plants. It is true that 

 Adolph Mayer in Germany, and Schlosing in France, have 

 experimentally shown that plants can take up nitrogen by 

 their leaves from ammonia supplied to them in the ambient 



