400 MR. R. RIGG'S EXPERIMENTS ON NITROGEN IN VEGETABLE PRODUCTS. 



ing these leaves sometimes to remain on the trees until they are very abundant, and 

 then removing a considerable portion thereof, leaving the rest to grow, we have at 

 intervals of very few days an opportunity of chemically examining this very import- 

 ant and indispensable part of vegetable production under very different circum- 

 stances. By carefully dissecting these leaves, we are enabled to discover by analysis 

 important changes produced in very few hours. From the proneness on the part of 

 these leaves to pass into decomposition, at favourable temperatures, we have a feature 

 brought before us which claims our best attention. And we have the fruit of this 

 plant affording us, in its conversion into wine and other substances, an opportunity 

 of examining into many important chemical changes, and I may add, of making the 

 accuracy of many popular theories more than questionable. 



The vines which more generally afforded me materials for examination are those 

 which produce the white and black sweet-water grapes. They are in the open air, 

 and are nailed to the south side of a brick wall. A series of experiments upon the 

 leaves of these vines are given in Table VII., showing in a striking manner that ni- 

 trogen is in large quantities when they first make their appearance ; that as they are 

 developed, it decreases in proportionate quantity ; that it is in excess during the pe- 

 riod of their most rapid growth ; and that towards the close of the year it is compa- 

 ratively small. 



Table VII. 



The first small leaves on the white "1 

 grape vine J 



Leaves from the same about a month 1 

 afterwards J 



Leaves from the same in July 



Leaves from the same in August .... 



Leaves from the same in November . . 



The first leaves on the black grape vine 



Leaves from the same in June .... 



Leaves from the same in July .... 



Carbon. 



37-7 



4-2-2 



39-8 

 39-1 

 41-9 

 41-8 



42-8 

 41-5 



Hvdr. 



0-5 

 0'4 



1-4 



Oxygen. 



4-2 

 6-1 



3-8 

 M 



Nitr. 



5-1 



5-3 



3-5 



2-9 

 2-3 

 7-8 

 5-4 

 3-6 



Resid. 



9-5 



3-8 



3-8 

 6-6 

 9-2 

 10-3 

 3-8 

 3-0 



Water. Total. 



47-2 = 100 

 48-3 = 100 



48-7 

 45-3 

 46-6 

 38-7 

 44-2 

 [50-8 



100 

 100 

 100 

 100 

 100 

 100 



Nitr. for 

 1000 Garb. 



134 



126 



88 

 74 

 55 

 185 

 126 

 88 



With a view of ascertaining whether or not these peculiarities in the chemical con- 

 stitution of the leaves of plants and trees were universal, I have had recourse to ex- 

 tensive analyses thereof, gathering the leaves from a great number of trees at different 

 stages of their growth. The results hereby furnished may be obtained from the ex- 

 periments in Table VIII. 



