196 OF FORCE. 



hence may be regarded as distinct in kind. There is no change of material in magnetic, 

 molecular or capillary attraction. The two last, though quite analogous, yet seem to be 

 distinct in kind. 



It is difficult to conceive how the growth of a body takes place. We see, under the 

 microscope, some of the stages of growth. Granules first appear in clusters, and it would 

 •eem that the formation of a single granule is the result of a chemical force : it is a mole- 

 cular force, perhaps, which brings a number of these granules together ; and here we ob- 

 •erve a phenomenon like one which belongs to an organ, the production of a vesicle on 

 one side, or in connexion with the cluster of granules. This vesicle becomes the cell ; an 

 individual capable of reproducing like cells with itself. If we suppose, then, in the spring, 

 when the sap of a plant or tree accumulates between the bark and wood, a granule to be 

 formed by a combination of elements, and then an aggregation of them by molecular force, 

 an organ of the lowest capacity is formed, and we may suppose a larger of these organs 

 is developed. In process of time this larger becomes the annual ring of wood. Endoge- 

 nous stems grow by the formation of wood upon the outside. But whatever kind of growth 

 it may be, the phenomena are the same, the granule precedes the cell ; and thus granules 

 may be formed at the extremity of the axis of a plant, and thereby lengthen it ; or it may 

 appear at points on the side of the axis of growth, and thereby extend the branches hori- 

 zontally ; or between the bark and wood, and thereby increase the diameter of the trunk ; 

 the process is the same, but the different results depend upon the position of the growing 

 points. 



It is instructive to inspect the form and combination of cells under the microscope. The 

 species of plants have their peculiar cells and arrangements. Even the species of the oak, 

 as numerous as they are, furnish differences by which the species may be determined. Cer- 

 tainly, when the oak, elm, chestnut and beech are compared, or the members composing 

 different families, the differences are too great to be overlooked. The separate and distinct 

 products are connected of course with these differences in the form and arrangement of 

 cells ; and I may recur to the maxim of Mulder, that form is the parent of change as well 

 as matter ; that it is a true force. Function is, therefore, connected with form and ar- 

 rangement ; matter, form and function must therefore be considered in connexion, and 

 they can not be separated from each other. As an illustration of the differences in the form 

 of cells, and of their arrangements, I may refer to numerous plates in the second volume 

 of the Agriculture of New-York. The resemblance of cells and combinations are much 

 closer in the corniferous stems than in the other families of trees. So, as we approach the 

 cellulares, the similarity increases ; and yet, even in cellular plants, in their structure 

 there is room for great diversity in form, size and arrangement, by which products of dis- 

 similar kinds may be produced. Two kinds of stimuli are required to exci(e or awaken 

 the force in seed or buds : heat and moisture are necessary to effect the first transforma- 

 tions, which are simply chemical, really simple results, but these precede a series more 

 complicated, when the directive force begins the arrangement of molecules of the fabric 

 to be constructed. 



