12 J. M. Macfarlane. — Nepenthaceae. 



the metaphloem, which becomes a cylindrical zone of considerable width. The metaxylem 

 develops the same elements as are to be treated of under the stem. 



Stem system. The anatomy of the stem was studied by Schultz and Kor- 

 thals, but more recently in a thorough manner by Zach arias. The following account 

 confirms, and only in some points extends his observations, specially as pertaining to 

 other species than those studied by him. Transverse sections of the stem of N. Hookeriana 

 through the first internode beneath the expanding leaf, show a shallow epidermal layer 

 with cuticularized walls. From it arise many multicellular hairs. Beneath are 3 — 4 

 layers of chlorophylloid cells with clear walls, succeeded by 12 — 14 layers of fibrous 

 cells. These contain a few chloroplasts, and their walls are strongly thickened at the 

 angles. Isolated spiral cells traverse the fibrous tissue at irregulär intervals. Beneath 

 this is a zone of loose cortex tissue, composed of very unequal cells. Some of the 

 smaller ones enclose small starch grains, some conglomerate crystals, a few contain 

 chloroplasts, and some are spiral cells of rather large diameter. The endodermis 

 (Fig. 5/") is a regulär layer of cells with thin walls. The cells contain small starch 

 grains. Internal to it are 2 — 3 angular small-celled layers, succeeded by a relatively 

 broad zone of large spiral cells, that are linked together by small thin-walled ones. 

 Though thus peculiarly modified, if we accept present histological classifications, this 

 double zone must be regarded as a highly specialized pericambial layer. The remaining 

 plerome tissue within the last, indicates commencing modification along various lines. 

 A relatively large amount in the centre is converted into pith tissue. This differentiates 

 in part into thin-walled cells, that later may become filled with starch grains, and into 

 large spiral cells. All of this tissue, as it continues to mature, so strikingly resembles 

 that of the cortex, as to suggest a common origin embryologically with it. But later 

 methods of wall thickening develop in the pith that cause it to differ strikingly from 

 the cortex, while the conglomerate crystal cells of the latter have no parallel in the 

 pith cells. The marginal mass of tissue beneath the pericambium differentiates into a 

 ring of cambioid tissue, in which arise the proto-rudiments of the bundles. These 

 are widely apart from each other, though they are connected by a ring of flattened 

 cambial cells. The number of bündle rudiments varies from 2 9 to 34, and each 

 bündle consists at first of a few spiral tracheae and companion cells internally, with 

 phloem cells and sieve tubes externally. But a noteworthy detail, not shown evidently 

 in the material used by Zacharias, is the formation of a set of pith bundles (Fig. 5) 

 out of Strands of meristem cells. The tissue that originates these is either part of 

 a wide cylinder, or of isolated Strands embedded in the pith, and made up of small- 

 celled elements, in the midst of which the bundles mature. Each of these pith bundles 

 is wedge-shaped, collateral, and consists of the usual elements. Their number varies 

 from 5 to 8, and while one or two may arise toward the middle of the stem, the 

 majority are disposed near or against the protomeristem zone. Growth in the normal 

 cambial ring gives rise to interfascicular tissue that fills up the areas between the 

 bundles, and to numerous uniseriate medullary rays, that run out between the vascular 

 masses formed. The vascular tissue consists of narrow elongated tracheids with pitted 

 lateral walls, of broad quadrangular indurated cells, and of pitted or porous vessels of 

 varying diameter. One to six rows of this tissue may intervene between each pair of 

 medullary rays. Division into annual rings of growlh, is as a rule impossible, since 

 tissue is laid down with perfect and more or less continuous uniformity. But the total 

 number of elements in depth, even in a three-year-old stem, is not great. During 

 the second year however, an interesting change takes place in the region of the peri- 

 cambium. The outer cells begin to divide, and cut off a typical cork tissue (Fig. §Bg') 

 composed of shallow pale-yellow cells, much resembling those of the root. This cork- 

 formation causes gradual shrivelling, browning and decay of all the tissue outside. By 

 the fourth or fifth year therefore, in such species as N. ampidlaria, N. gracilis etc. 

 this decaying tissue composed of epidermis, fibrous and cellular cortex, and endo- 

 dermis, bursts lengthwise, then transversely and finally scales off. In such species as 



