Finlayson. — Stem-structure of Leafless Plants. 363 



tissue is composed of granular phloem parenchyma (fig. 3c, 

 p. par.), whose cells appear roundish in transverse section, 

 and a few sieve-tubes with transverse plates (fig. 3c, s. t.). 

 There is a well-developed cambium of 4-5 layers of small, 

 squarish, transversely elongated cells containing conspicuous 

 nuclei. 



The xylem forms more than half the thickness of the 

 entire vascular bundle. There are but few true vessels, one 

 or two spiral and one or two pitted, in each bundle ; the 

 greater part of the xylem tissue is composed of libriform cells. 

 In transverse section these appear as polygonal cells with 

 very thick walls, and fitting closely into each other. In a 

 longitudinal radial section (fig. 3c) they are seen to con- 

 sist of greatly elongated cells, with oblique end walls which 

 dovetail into each other. The thickened cell-walls have thin 

 spots both on longitudinal and transverse walls by which they 

 can communicate with each other. The true vessels occur in 

 the inner part of the vascular xylem. 



The pith-cells, which occupy the centre of the stem, are 

 smaller on the outside (next to the xylem) and larger in the 

 centre of the stem. They are polygonal, thin-walled, about 

 as long as they are broad ; those next to the xylem contain a 

 great many starch-grains (in winter), while those in the centre 

 have only a few starch-grains. 



The older stems and spines become dry and scaly ; only 

 the younger can assimilate. The most remarkable features 

 about the structure of the stem are the double epidermis, 

 the great development of chiorenchyma and of woody cells, 

 and at the same time the small number of true vessels in the 

 wood. The two former are evidently intimately concerned 

 with the work of assimilation, and the latter with the ques- 

 tion of rigidity. The abundant palisade chiorenchyma facili- 

 tates assimilation, while the libriform cells give the stem the 

 rigidity and at the same time the elasticity so necessary to a 

 plant which is often exposed to wind. 



Clematis afoliata, Buchanan. 



Hooker does not mention this species in the "Handbook 

 of New Zealand Flora," but T. Kirk, in the " Students' Flora 

 of New Zealand," mentions it on p. 3. He says its habitat 

 is " Middle Island : Nelson, Marlborough, Canterbury, and 

 Otago ; but local." It belongs to the order Banunculacece. 

 In other species of the same genus the leaves have a long 

 petiole ; in this species only the petiole is present — at least, in 

 the adult plant. The petioles arise in pairs from a node, each 

 pair being at right angles to the pair above it; the internodes 

 are very long (about 7 in. in older shoots). The young shoot 

 arises in the axil of the petiole, with the inflorescence at its 



