274 NITROGEN. [BOOK n. 



that those seeds of the same kind, which contain the largest 

 quantity of nitrogen, germinate the earliest. Alburnum he 

 finds to contain more nitrogen than duramen, and fast- 

 growing timber more than slow-growing, whence he infers 

 that nitrogen exercises its influence in causing decomposition. 

 The latter opinions he considers to be rendered still more 

 probable by the proportion of nitrogen found in different 

 species of wood, cateris paribus : thus in satin wood and 

 Malabar teak, both timber of great durability, the quantity 

 of nitrogen is almost inappreciable ; in Dantzic and English 

 oak, the quantity is also very small ; in American birch which 

 soon decomposes, nitrogen is found in large quantities. Mr. 

 Bigg finds nitrogen in large quantities in Vine leaves when 

 they first make their appearance : as they are developed it 

 decreases in proportional quantity; is in excess during the 

 period of most rapid growth, and towards the close of the 

 year it is comparatively small. He states the full-blown 

 petals of the Rose to contain 24 parts of nitrogen in 1000 of 

 carbon, while the unexpanded and central petals contain 66 

 parts. Mr. Rigg has also considered the evolution of nitrogen 

 during the growth of plants, and the sources from which they 

 derive that element. He states that his enquiries all tend to 

 prove that nitrogen is evolved during the healthy perform- 

 ance of the functions of plants ; that the proportion which it 

 bears to the oxygen given off is influenced by the sun's rays ; 

 but that owing to the necessary exclusion of the external 

 atmosphere during the progress of experiments, it is impos- 

 sible, with any degree of accuracy, to calculate the volume of 

 these evolved gases during any period of the growth of plants 

 in their natural state. If to this indefinite quantity of 

 nitrogen given off by plants, there be added that definite 

 volume incorporated into their substance, the question arises, 

 whence do plants derive their nitrogen, and does any part of 

 it proceed from the atmosphere ? This problem Mr. Rigg 

 has endeavoured to solve by a series of tabulated experiments 

 upon seeds and seedling plants, the result of which is a large 

 excess of nitrogen in the latter, and under such circumstances 

 of growth that he is compelled to fix upon the atmosphere as 

 its source. He has also arrived at the conclusion, that the 



