AGRICULTURAL CHEMISTRY. 



133 



ways, essential to the perfection of the plant; for in its absence seeds 

 cannot germinate, flowers cannot yield fruit, and fruits cannot ripen. 

 In germination the larger bulk of the seed, the cotyledons, by the 

 absorption of oxygen, are disorganized and converted into structure- 

 less and soluble bodies, which become the food of the smaller part of 

 the seed, the embryo, and by its vital operations are again organized 

 as the young plant. In the process of flowering, matters stored in 

 organized form in other parts of the plant are transported to the 

 blossom to serve for its rapid development. The flower itself cannot 

 absorb food from without; and in the transformation of the already 

 elaborated food from the stem and leaves of the plant into the new 

 forms required by the flowers, oxygen plays an essential part. The 

 reawakening of life in the tree at spring time, and the ripening of 

 fruits, are accompanied with changes of a similar character, and from 

 them result many oxydized products. Vegetable physiologists have 

 furnished microscopic evidence that similar alternations of the orga- 

 nizing and disorganizing processes take place in the individual cells, 

 so that we are warranted in assuming that oxygen (whether that of 

 the free atmosphere or that evolved in the cells themselves is in- 

 different) plays an important and unceasing part in the development 

 of vegetation. 



Nitrogen in the free state also appears to be incapable of direct 

 assimilation. Within a few years the subject has been studied by 

 various investigators, but with contradictory results. Ville, of Paris, 

 in 1853, published a volume describing his experiments, which led to 

 the conclusion already arrived at by Priestley, in 1779, viz: that 

 nitrogen is assimilated. Other investigators, however, by means of 

 trials carried out under conditions less complicated and more adapted 

 to yield reliable evidence, have uniformly been conducted to the 

 opposite view. 



Especially to Boussingault do we owe a most careful investigation of 

 this question. His plan of experi- Fig. 9. 



ment was simply to cause plants 

 to grow in circumstances where, 

 every other condition of develop- 

 ment being supplied, the only source 

 of nitrogen at their command, be- 

 sides that contained in the seed it- 

 self, should be the free nitrogen of 

 the atmosphere. For this purpose 

 he prepared a soil consisting of 

 pumice stone and the ashes of clover, 

 freed by heat and acid from all 

 compounds of nitrogen. This soil 

 he placed at the bottom of a large 

 glass globe, (see figure 9,) of 15 to 

 UO gallons capacity. Seeds of cress 

 or of other plants were deposited in] 

 the soil, and pure water supplied to' 

 them. After germination, a small 

 glass vessel (D) filled with carbonic acid (to supply carbon) was secured 



