CAMBIUM. 



[ 107 ] 



CAMPIUM. 



CAMBIUM. The name applied to the 

 young cellular layers from which the woody 

 structures of plants are developed. When 

 we make sections near the growing points 

 of any stems, as in terminal or axillary buds, 

 we find a quantity of extremely delicate, slen- 

 der, elongated cells, distinguished from the 

 generally rounded cells of the parenchyma, 

 and forming rudimentary cords in the situa- 

 tion of the future woody and vascular bun- 

 dles. In the Dicotyledons, they stand in a 

 circle, so as to separate the apex of the pith 

 from the young bark ; the ring may be seen 

 in cross sections a little below the growing 

 point. At the very apex of the stem all the 

 tissues merge into the delicate universal ge- 

 nerative tissue. In the apex of Monocotyle- 

 donous stems, and also those of Ferns and the 

 higher Flowerless plants, the cambium isfound 

 in delicate cords imbedded in the nascent 

 general parenchyma, indicating, even in this 

 early condition, the position and arrange- 

 ment of the isolated fibrous and vascular 

 bundles. Sections of the outer region of the 

 stem of Dicotyledons demonstrate the exist- 

 ence of a layer of cambium at the outer sur- 

 face of the youngest wood, which indeed 

 passes gradually into the cambium. This 

 cambium is the tissue from which the suc- 

 ceeding layers of wood are generated, and its 

 position on the outside of the fibro-vascular 

 bundles gives these their indefinite power of 

 development. The cambium of the Mono- 

 cotyledonous bundles becomes enclosed be- 

 tween the wood and vessels of individual 

 bundles so that their growth is limited. The 

 cambium of the outside of the wood of Di- 

 cotyledons forms new layers of liber, in most 

 cases, on the inside of the old ones, pari 

 passu with the development of the layers of 

 wood. Cambium, which is in great part only 

 an early and transitional form of cellular tis- 

 sue, afterwards to become developed into 

 wood, is composed of delicate cellulose 

 cells enclosing a primordial utricle, nucleus, 

 and abundance of nitrogenous protoplasm, 

 but usually without chlorophyll. The cells 

 multiply by transverse subdivision in the 

 elongation of the stem, and by perpendicular 

 division (tangental and radial) as the stem 

 expands in diameter. This process is effected 

 by the constriction of the primordial utricle 

 and gradual development of a septum, as in 

 ordinary vegetative cell-development. The 

 cambium of most Dicotyledons is gradually 

 matured into wood, from within outwards ; 

 but in the Monocotyledons and Flowerless 

 Cormophytes it often remains in great part 



in a delicate and soft condition, forming 

 what are called by von Mohl the vasa pro- 

 pria, or proper vessels. Owing to the deli- 

 cacy of its structure, cambium was formerly 

 imagined to be a thick mucilaginous fluid 

 poured out in the growing regions of plants 

 (as between the wood and liber of Dicotyle- 

 donous stems in spring), which by degrees 

 became organized and converted into cellular 

 tissue, by the independent origin and subse- 

 quent coalescence of a number of cells gene- 

 rated in this fluid. This view, founded on 

 imperfect observation, was strongly supported 

 by Mirbel and others. 



BIBL. Treviranus, Physiologic der Ge- 

 w'dchse, i. 159; Mirbel, Nouvelles notes sur 

 le Cambium, Ann. des Sc. nat. 2 ser. xi. 321; 

 Notes sur le Composition du Cambium, Ann. 

 des Sc. nat. 2 ser. xix. 197; Payen, Comptes 

 Rendus, 1839, 509; Schleiden, Grundzuge 

 der Botanik (Principles of Botany}; Henfrey, 

 Outlines of Structural Botany ; Nageli, Zeit- 

 schrift. fur Wiss. Botanik, iii. 64; Mohl, Die 

 Vegetabilische Zelle (The Vegetable Cell, 

 Transl. London, 1853); Schacht, Die Pflan- 

 zenzelle, Berlin, 1852. 



CAMBRIC. This name was formerly ap- 

 plied strictly to the finest kind of linen cloth. 

 It is used now in a loose sense in trade. 

 French cambric, however, ought to be linen. 

 Scotch and English cambrics are now com- 

 monly made of cotton, while Indian cambric 

 is made of the grass-cloth fibre. The fibres 

 may be distinguished under the microscope, 

 and the value of the fabric thus ascertained. 

 See FIBROUS SUBSTANCES and COTTON. 



CAMERA LUCIDA. INTRODUCTION, 

 p. xix. 



CAMPANULARIA, Lamarck. A genus 

 of Polypi, of the order Anthozoa. 



Char. Polypidom rooted, creeping, or 

 when compound, erect ; the main tube fili- 

 form, continuous, giving off its pedunculated 

 cells irregularly or in whorls; peduncles 

 ringed, usually long; cells campanulate; 

 vesicles scattered, sessile; polypes hydri- 

 form. 



7 British species : 



C. volubilis (PL 33. fig. 4). Stem a single 

 tube, creeping, filiform ; cells on long, slen- 

 der, ringed peduncles, campanulate, with a 

 serrated margin; vesicles ovate, wrinkled 

 concentrically. 



Parasitic on sea-weeds, &c.; frequent. It 

 forms an elegant microscopic object. 



BIBL. Johnston, Brit. Zoophytes, 1847. 



CAMPIUM, Presl. A genus of Acrosti- 

 cheae (Polypodaeous Ferns). Exotic. 



