VE(iKTAl{I,E niYsioLoay. 



of vcirctablcs. riiilosopliers liavt- jiivcir so much altciition niid research to tlic 

 motion of the heavenly botlies, ami made tliemselves so well ae(|uuiiite(l with the 

 laws jroverninp; the same, as to l)e able to predict the time and place of the appear- 

 ance of a hitherto undiscovered jilanct. The tlieory of the circulation of the blood, 

 and of nutrition, is believed to corresjiond very nearly to the laws of its govern- 

 ment, and will account for the varied ))henomcna wo witness. The science of 

 vcii:ctable i)hysiolofry, being of later origin, may be said to have not yet reached 

 that degree of jicrfection of which it is capal)le, nor so fully to correspond to the 

 facts bearing upon it. 



When ])hiloso|)hy began to turn its attention to the circulation of the sap, and 

 the growth of vegetable matter, and to form a theory of its laws, the circulation 

 of the blood in the animal economy, and its laws of nutrition, were suj)posed to 

 present a parallel case so nearly allied, as to l)c taken as the type of tlie law in 

 that case. The fact of the circulation of the sap from the roots to the leaves, and 

 the proof that carbonic acid gas was iml)il;ed l)y them, while water and oxygen gas 

 was given off, seemed to point strongly to the conclusion that the leaves acted to 

 the vegetable in a similar manner to what the lungs did in the animal. It was 

 believed that the carbonic acid and other substances were taken up by the roots 

 ill a fluid or gaseous state with the sap, and then carried by it to the leaves, where, 

 being exposed to sunlight in their Itroad surfaces, a decomposition or change took 

 l)lace, making these materials organizable, or ready to be assimilated by the plant. 

 This newly i)repared matter was now supposed to descend between the bark and 

 the wood, and to be deposited as growth, thus carrying out the parallel between 

 the animal and vegetable economy. This parallel is beginning to be seen not to 

 exist to the extent it was once thought. Professor Gray, in his Botanical Text- 

 Booh, says "there is no circulation in plants similar to that in animals." 



In the last number of the last volume of the JlurticuUurist (page 555), is an 

 article on the "True Theory of Grafts." In this article, Dr. Lindley's "own 

 words" are directly applicable to the case. " It is, however, now certain," he 

 says, " that although wood is formed by a descending process, yet that its descent 

 is not in an organized state. Fluid matter — out of which it is produced — passes 

 indeed from above downwards, but the formation itself is wholly local and super- 

 ficial, and, consequently, there is no such thing as an incasement of the lower 

 part of a tree by wood descending from above." This " important fact," as he 

 terms it, receives " a new demonstration" from the experiment of " Dr. Maclean," 

 who, in grafting a white* beet on a red beet, ".and vice versa,'''' showed that there 

 was no " blending of the two colors," but that the growth of the white part made 

 white growth, and of the red part made red growth, whether the root from which 

 it received its sap was red or white. Thus jiroving, that of each ]iart "its own 

 cells produced its own coloring matter as they formed superficially.", "This is 

 entirely consistent," says the writer of the article alluded to, "with all that has 

 been discovered by the modern })liysiologists who have applied themselves to a 

 study of the natue of the individual cells of which plants consist." 



Admitting these ])Ositions to be true, and "that each cell has its own inherent 

 power of secretion," and that "fluid matter out of which wood is produced," is 

 " not in an organized state" in its supposed downward descent, it may be asked, 

 where is the necessity for such " descending process" at all ? What advantage 

 is gained by the " fluid matter" being carried to the leaves, as is supposed, if, in 

 its descent, it is not organized, but that " each cell has its own inherent power of 

 secretion," and " perseveringly retains that which is natural to it?" Indeed, 

 are strong reasons for believing that there is no such downward process 

 Where is its evidence ? where is the necessity for its existence ? It has " 



