Imijortance of Nitrofjenous Manures. 



81 



Fragment of the confervoid substance developed from 

 tiie spores of a Moss, showing the mode of origin of 

 a leat'-biid, from a branch-cell of the filament, mag- 

 nified 2u0 diameters, a, b, c, fragments of the fila- 

 ments, sliowing successive stages of growth; in c, 

 the leaf-bud is formed. 



In the formation of the cell which is to be developed into the 

 rudimentary plant (called the embryo), in the seeds of all 

 flowering- plants, only part 

 of the contents of the parent- 

 cell are used for the new 

 cell ; a small quantity of the 

 protoplasm is gathered up 

 into a little ball at one end of 

 the large parent-cell, and, ac- 

 quiring a membrane, lies as 

 a little loose bag there for 

 some time, and then begins 

 an independent course of 

 growth : so that the new 

 rudimentary plant is not tixed 

 in any way but only enclosed 

 in the seed. 



We have dwelt at length 

 upon these points, because 

 they are of the highest im- 

 portance in vegetable physiologv. The knowledge of the 

 dependence of the process of growth upon the gelatinous lining 

 of the cell (the formative layer or primordial utricle, and the 

 protoplasm) explains at once the influence of manures con- 

 taining animal matter, or other nitrogenous substances. These 

 contents of the cell ai'e the really active living structure, which 

 resides in the outer membranous case like a mollusk in its shell, 

 and they are composed of su Instances closely analogous to animal 

 matter; in fact, are the parts composed of albumen, flhiine, 

 caseine, gluten, «S:c. The activity of the growth of a plant depends 

 mainly upon the free supply of nitrogenous substance for the 

 increase of this protoplasm. Plants can indeed appropriate nitro- 

 gen from the ammonia, and perhaps dirccthj from the air of the 

 atmosphere in their natural state ; but the effect of increased 

 supply of nitrogenous food is most strongly marked in all plants 

 brought under cultivation. Tlie influence of nitrogenous manures 

 can scarcely be questioned by any who is accustomed to observe 

 their effects upon the esculent vegetables cultivated for the mai'kets 

 of London and other large cities. By the help of organic manure 

 and contrivances to increase the heat or prevent the cooling of 

 the soil, vegetaldes are made to grow even to some extent iude- 

 j)('ndently of lujht, which we know to be of j)rime importance to 

 vegetation in a state of nature. That plants can grow inde- 

 pendently of light the botanist already knows, from the pheno- 

 mena so familiar to him in the vegetables of the class of Fungi ; 

 and it is most important to bear in mind, when considering tliis 

 VOL. XVI [. 



