12 SYLVA AMERICANA, 



effects and preserves plants, being in a liquid or aereform state, 

 it is wonderfully contrived that there should be an organic 

 vascular system for its distribution, and that it should likewise 

 possess the vital power of assimilation, in order to effect and 

 perpetuate the growth which takes place, and to diversify the 

 products which characterize the innumerable variety of plants 

 which constitute the vegetable kingdom. 



General Texture of Plants. 



Much light has been thrown upon the general texture of 

 vegetables, by the uuc -cKcopic figures of Grew, Malpighi and 

 others, but more especially the observations and highly magnified 

 dissections of M. Mirbel. From preceding writers we have 

 learned the general tubular or vascular structure of the vegetable 

 body, and the existence of some peculiar spirally-coated vessels 

 in many plants. On these slender foundations physiologists 

 have, at their pleasure, constructed various theories, relative to 

 the motion of the sap, respiration and other functions, presumed 

 to be analogous to those of animals. The anatomical observations 

 of Mirbel go further than those of Grew, &:c., and it is necessary 

 to give a short account of his discoveries. 



He finds, by the help of the highest magnifying powers, that 

 the vegetable body is a continued mass of tubes and cells ; the 

 former extend indefinitely, the latter frequently and regularly 

 interrupted by transverse partitions. These partitions being in 

 the corresponding cells, and each cell increasing somewhat in 

 diameter after its first formation, except when restrained by the 

 transverse partition, seems to account for the hexagonal figure.* 

 The membraneous sides of all these cells and tubes are very 

 thin, more or less transparent, often porous, variously perforated 

 or torn. Of the tubes, some are without any lateral perforations, 

 at least for a considerable extent; others pierced with holes 

 ranged in a close spiral line ; in others several of these holes run 

 together, as it were, into interrupted spiral clefts ; and in some, 



* For illustrations of this part of the subject., see Plate I. 



