592 Remarks on MirbeVs 



Art. IV. Remarks on MirbeVs " Nouvelles Notes sur le Cambium" 



extracted from a Work on the Root of the Date Palm. By James 



Main, A.L.S., &c. 



M. Mirbee has been long known as an eminent vegetable physiologist. 

 He was the first who, from various experiments executed with the greatest 

 care, was able to give a rational account of the manner of the annual accre- 

 tion of dicotyledonous steins. He proved the truth of the discoveries of both 

 Grew and Duhamel, namely, that the cambium was a distinct member of a 

 tree, and that it was that substance whence all the annual growths proceeded : 

 in other words, that every new member existed, in the first stage of its identity, 

 in the state of what is called cambium. 



It may be necessary to state that the member of a stem which is known by 

 this name is always visible, during the summer months, between the bark and 

 the former year's alburnum. From the commencement of the growth in the 

 spring, up to the months of July or August, it is of a mucilaginous whitish 

 substance, and is, in fact, the new layer of wood increasing from its thin co- 

 lourless state in winter, to its perfect bulk, hardness, and organised form of 

 timber, which takes place sooner or later in autumn. This is a fact which is 

 not only insisted on and clearly proved by M. Mirbel, but by every person 

 in the least acquainted with the physical structure and annual growth of dico- 

 tyledonous stems. 



Now, as that change of mucilaginous matter into perfect timber is an esta- 

 blished fact, M. Mirbel, it seems, had a great desire to discover, by observa- 

 tion, how, or by what gradations, this remarkable change took place. He 

 states that he was constantly engaged in the study of this hidden process : 

 and at last found, accidentally, a good opportunity of observing the growth 

 and changes of the cambium on the roots of the date tree (Pbce'nix dactylifera). 

 He does not say where he met with such a subject ; but it was, probably, one 

 in a hot-house of the Jardin des Plantes, of which garden, we believe, he is 

 director. He cut a root of this palm transversely, and, with a properly ad- 

 justed microscope, observed the subsequent enlargement of the cambium in 

 its movement towards closing the wound, or in its swelling to increase the 

 diametric bulk of the root. 



Previously to this examination, M. Mirbel had considered the cambium to be 

 only mucilaginous, or a simple cellular body, especially in the earlier stage of 

 its visible existence : but, during this examination, his glass showed that it 

 was much more highly organised ; containing not only cells, but various ves- 

 sels (utricules), as well as real or apparent lines variously disposed. 



By constantly inspecting the gradual developement, M. Mirbel moreover 

 noticed that the cambium, when first protruding or extending itself, appears 

 with a mammillary surface; "or, at least, itappeared such." These mamma?, 

 or granules, as other writers call them, make their appearance after the cellu- 

 lar organisation is visible ; he also noticed and describes several curious trans- 

 formations of the cells into vessels, the source whence they proceed, and their 

 final stations and appearance ; together with the thickening or shrinking of 

 the walls or partitions (cloisons) of the vessels ; the ultimate density and 

 gradual hardening of the exterior parts. The whole investigation is particu- 

 larly interesting, especially to those who wish to look beyond the surface of 

 things, and to have accurate ideas concerning the phenomena of vegetable 

 developement. 



Such discoveries are only practically useful, as showing that the cambium 

 is an organised body, even when it first appears with not greater consistence 

 than a " solution of gum Arabic ;" and that it is not a fortuitous accumulation 

 of the descending sap. 



Had M. Mirbel's very patient investigation no other result than setting us 

 right on this point of vegetable physiology, his labours would have been highly 

 creditable to him as a philosopher ; for it is well known that hardly two, of all 

 those who have written on the subject, agree in opinion. Grew's ideas have 



