412 Vegetable Physiology. 



persistent evergreen foliage may have some influence in pro- 

 ducing the abundance of highly-carbonised secretion. 



It is now time to look back over the particulars which have 

 been expounded in the foregoing pages, in order to see how far 

 we are enabled to draw from them any general physiological 

 conclusions. One thing strikes us at first sight — the absolute 

 necessity of entering upon the examination of the phenomena 

 in their microscopic detail, — since we have found that even the 

 simply chemical, like the vital, processes take place in what we 

 have termed the organic or physiological " atoms," the cells. 

 Each of these is a little apparatus in itself, executing its special 

 duties in more or less close association with its fellows, and the 

 physiological functions of the plant represent the sum of the 

 diverse actions of a multitude of these, which Ave have seen to 

 be more and more limited to special or individual operations in 

 proportion to the variety existing in their organisation and 

 arrangement. For this reason it is requisite to devote the 

 greatest attention to these minuticc of the appearances and 

 changes in the contents of cells, which have been described at 

 some length in the present paper. Only through an intimate 

 knowledge of the phenomena presented in the actively vegetating 

 cells, can we hope to arrive at a clear comprehension of the essen- 

 tial facts, and the general laws of the nutrition of plants. 



The accounts of the mode of development of cells given in our 

 former paper (vol. xvii. p. 62), and of the formation of the various 

 products of the cell described in the preceding pages, demon- 

 strate the extreme importance to vegetable life of those prin- 

 ciples commonly called " albuminous," characterized by a definite 

 composition into which nitrogen enters. These, which the chemist 

 distinguishes into albumen, fibrine, legumine, &c., the micro- 

 scopist recognises, under the name of protoplasm, as the seat ot 

 the vital activity of the plant, whether evinced in growth or in 

 the assimilation of nutrient substances. On a former occasion we 

 found them reproducing the cells themselves ; in the present 

 paper it has been shown that not only is the cell-membrane pro- 

 duced by their agency, but that they form the basis of the chloro- 

 phyll-granules, produce starch, oils, colouring matters, and ap- 

 parently also the soluble matters of the watery cell-sap. And 

 not only do they produce all these things, but they have the 

 power of decomposing and reconstructing almost all of them, as 

 may be required by the local or temporary exigencies of the plant^ 

 so that they form a sort of centre or medium with wliich all the 

 processes of vegetation are more or less directly connected. 



We may venture to suppose, therefore, that the ternary sub- 

 stances, the cellulose and starch, «Scc., series, are produced through 



