Nouvelles Notes sar le Cambium. 593 



been fully proved by Mirbel. Those of Linnaeus, Knight, Du Petit Thouars, 

 Poiteau, &c, are only seemingly theoretical fancies. A living author thus 

 expresses himself: — " The cambium is not a simple and homogeneous sub- 

 stance ; and, if in the animal system, bone always finds bone in the same blood, 

 and muscle always muscle, so, in the vegetable system, bark may always find 

 bark in the same cambium, and wood always wood. The organised and living 

 molecule abstracts from the alimentary mass such particles as are suited to its 

 own developement, and always produces its own type." 



The first line of this quotation accords with what has been proved by M. 

 Mirbel ; but all that follows is a transcendental assumption, which the writer 

 would find it as difficult to explain, as his readers to understand. Besides, 

 explaining vegetable developement by reference to that of animals is neither 

 philosophical nor satisfactory : there may be some analogy between the blood 

 of animals and the sap of plants, but it is so very distant, that nothing certain 

 can be elicited by a fancied comparison. 



In the course of M. Mirbel's investigation, he observed what has been 

 noticed by other vegetable anatomists, namely, that a single cell is capable of 

 being resolved into several others, by the splitting (dedoublent) of the walls ; 

 that is, the outside of the wall or case of the cell is like a lining sloughed off 

 and inflated, to form another cell in the direction of the growth. Every cell, 

 it seems, is so constituted ; and this property of division and subdivision has 

 given rise to the common saying, when treating of these matters, that each 

 member can produce " its own type : " yet, by division, be it remembered, 

 but not by abstraction of congenerous particles which float in the alimentary 

 mass, as intimated in the above quotation. 



The constitution and manner of developement of the cambium were the 

 principal objects which M. Mirbel had in view ; and these he has observed and 

 described with great minuteness. The root of this palm, he says, consists of 

 three distinct members, apparent on a transverse section ; and which he 

 denominates the peripheric, the intermediate, and the central. At a certain 

 stage of the growth, the outer member is separated from the intermediate 

 by a thick layer of cambium, which appears insulated ; there being no per- 

 ceptible union of it with the opposing sides of the members between which 

 it is contained. It was also observed that, during the growth, it is constantly 

 extending itself laterally, giving off parts both to the central and circumferent 

 members ; showing not only that the cambium is the source of all accretion 

 in the roots of the date palm, but that the process is somewhat similar to that 

 by which it divides itself into wood and bark on the stems of dicotyledonous 

 plants ; the inner and larger portion being changed into wood to increase the 

 axis, and a less portion thrown off as liber to thicken the bark. 



If we have understood our author rightly, it appears that the members and 

 manner of growth of the roots of the date are not much unlike those exhi- 

 bited in the stems of dicotyledons ; except that the latter has an addi- 

 tional member, namely the pith. The increase or thickening of the roots 

 of both are certainly very similar. The amplification of the stems is, 

 however, very different ; though both are centrifugal, that is, increasing 

 outwards : for, while the monocotyledon is enlarged by a uniform process 

 from the centre, the dicotyledon acquires diametric bulk by annual or 

 periodical gradations ; and it is the manner in which these additions are 

 made that was the special object of M. Mirbel's investigation, and which he 

 has so minutely described. 



It is to be regretted, perhaps, that our profound author has not decidedly 

 adverted to the origin of the cambium ; that is, from what other member it 

 proceeds. He says it is organisable matter; that it is always seen between 

 two other members which it serves to increase ; but he does not expressly say 

 whence it proceeds. 



Linnaeus thought it was produced by the pith ; Grew, that the liber and 

 wood were deposited at the same time in a single mass, which afterwards 

 divided in two, the one part adhering to the centre, and the other to the 



