GIVEN OFF BY PLANTS DURING THEIR GROWTH. 



57 



The indications of these Tables are certainly not without the 

 appearance of discrepancy, yet when we remember the circum- 

 stances of irregularity of growth already fully detailed, and also 

 the greatly varying products, of which the substance of the 

 plants is in several cases made up, the general uniformity of the 

 figures is sufficiently sinking, and calculated to lead to the ex- 

 pectation of much more definite results in future, and more care- 

 fully conducted experiments. 



Referring first to Table VIII. , and taking the upper section of 

 it, we see that the amounts of dry matter produced to 100,000 

 grains of water given off by the plant, range in the case of the 

 wheat, the barley, the pea, and the clover, in the unman ured 

 soil, between 371 and 404 grains; or, excluding the clover, 

 between the latter number and 386 grains, an approximation 

 sufficiently indicating some definite relationship between the 

 passage of water through the plants and the fixation in it of some 

 of its constituents. The bean in this series seems to be an ex- 

 ception, the amount of dry substance produced in this case being 

 about 479 grains, or nearly one-fourth more than the average of 

 the other unmanured plants. When we remember, however, the 

 much larger amount of nitrogenous compounds which this pro- 

 duct would contain than any of the other specimens, we see 

 that with this variation in the amount of vegetable growth 

 to a given quantity of water evaporated, there is, at least, coin- 

 cident variation in the composition of the product itself; and 

 the particular facts would lead to the suspicion that the water 

 evaporated had a more definite quantitative relationship to the 

 fixation of the ftcw-nitrogenous than to that of the nitrogenous 

 constituents of the plants. 



Looking at the results of the 2nd Series (with mineral 

 manure), we see a generally higher amount of dry substance pro- 

 duced for a given circulation of water than in Series 1 ; and 

 also, the barley excepted, a much greater uniformity than in the 

 former Series. The cause of this discrepancy in the barley may 

 perhaps be explained by the fact already mentioned, that the lid 

 of the jar in which it grew had been broken during a consider- 

 able period of the experiment ; and though the pieces were 

 cemented together, yet it is more than probable that water 

 was lost from the soil by evaporation through the crack, in 

 which case the amount of product would necessarily appear 

 low. 



In the case of this Series too, it is seen that the product of 

 beans is exceeded by the peas, and nearly reached even by the 

 wheat. On the view referred to above, therefore, it would be 

 necessary to suppose that, provided the results are to be relied 

 upon, the composition of the several products as regards nitrogen 



