298 FLOEA ANTARCTICA. [Fuegia, the 



Anatomy of the stem. A branch of this species, after attaining the age of two years and upwards, consists 

 principally of a soft white cellular tissue, occupying the axis of the plant and communicating with the thick bark by 

 means of broad medullary rays. The latter are separated by woody plates, disposed in two concentric series, and 

 formed almost entirely of scalariform tissue with sometimes pleurenchyma. Cuticle. This is very stout in texture : 

 in a first developed branch it consists of only one row of small cells (Plate CYII. bis, f. 11) these must be rapidly 

 added to, for after another year the cuticle of the same branch is of much greater density and formed of many series 

 of cells, much blended together, though not so completely as to assume the appearance of a homogeneous tissue 

 without any trace of cellularity, which it afterwards attains (Plate CYII. Jiff. 4, 5, and 6). The cuticle is devoid 

 of stomata commonly so called, but furnished with numerous longitudinal prominences, each marked by a fissure. 

 A transverse section of one of these is given at Plate CV1I. /. 4, where the appearance is as of several layers of 

 cuticle superimposed and forming the prominence, becoming cellular towards the centre, and depressed, pushing 

 the subjacent epiphlceurn before it. There is no actual stoma or communication between the external atmos- 

 phere and tissue of the bark, further than what may be supposed to be afforded by cellular tissue, which is a 

 rapid conductor of moisture. These are very evident in the branches of the second year, no doubt answer to 

 stomata, whether performing the same functions or no, and are an instance either of the cuticle retaining its 

 originally cellular organization at the point where they occur, or reverting to that structure. 



Bark. This is composed almost entirely of a mass of cellular tissue, shrinking much when the stem is dry. 

 The epiphlocum is formed of several rows of transversely elongated thick-walled cells, it occasionally contains air- 

 cavities, but these are not so numerous or conspicuous as in M. punctulalnm. The vessels of the liber are disposed 

 about half way between the cuticle and wood, are often very inconspicuous and formed of scattered bundles of fibres 

 (Plate CVII. /. 5 and 6 a.) protected by very thick-walled cells, as in most, if not all, the Loranthacea, at other 

 times they are in two series or variously disposed. This tissue does not appear to pass from one internode to 

 another, but to be' interrupted at each articulation, as M. Decaisne found to be the case in Viscum* The paren- 

 chyma between the vessels of the liber and wood is often dense, sometimes but rarely these vessels are seen to 

 be immediately in contact with the wood as at Plate CVII. /. 5 and 6 b. Wood. Within the bark are arranged 

 two concentric series of woody plates or wedges, these two series are separated by a zone of cellular substance, and 

 are generally arranged with tolerable precision : besides these the pith of the plant is intruded upon by other 

 wedges or bundles of vascular tissue, unsymmetrieally disposed, one of them often occupying the axis itself. Each 

 wedge or plate is composed principally of concentric layers of very large vam scalariformia, becoming more densely 

 packed and much smaller in diameter towards the axis of each layer, where they are almost invariably furnished with 

 a spiral filament. Between the layers of the first three or five years there is generally deposited two bundles of 

 pleurenchyma similar to that of the liber, one on each side (Plate CVII. ter, f. \.f) but between the more recent 

 layers there intervenes only the more delicate vascular tissue (/. 1 arid 2. e) : as mentioned above, however, pleu- 

 renchyma is sometimes more copiously deposited between every layer, as at Plate CVII. /. 5 and 6, b. The 

 narrow portion of each wedge invariably rests on a mass of pleurenchyma (Plate CVII. ter, f. 1. y,) deposited at 

 the same time as the fibres of the liber c, that is during the first year, as in the common Misseltoe. The wedges of 

 wood belonging to the second series are smaller than those of the first, but similarly formed in all respects, and 

 consisting of as many layers, though the inner are very inconspicuous. 



The pith consists of cellular tissue similar to that of the liber, and is very lax even in the older stems. 



The transverse section of this stem, appears at first sight to differ very remarkably from that of most exo- 

 genous plants ; this arises from the wood being deposited in two concentric series, separated by a broad zone of 

 parenchyma, from the great breadth of the medullary rays, the irregular distribution of the fibres of the liber 



* Decaisne, Memoire sur le developpement du Pollen &c. du Gui, in Act. Acad. Roy. de Bruxelles, p. 49. 



