Betts. — Autecology of Plants of Peridotite Belt, Nelson. 235 



The phloem forms a wide band in which the elements are very regularly 

 arranged. Most of the parenchymatous cells of the phloem contain tannin. 

 The xylem consists chiefly of wood-fibres of small diameter ; these have 

 very thick walls and small lumen. The number of vessels is small in com- 

 parison with the amount of wood, and they are not of wide diameter. 

 The medullary rays are numerous and uniseriate ; the cells have lignified 

 walls, and contain tannin. The pith is solid, and consists of polygonal or 

 roundish cells with pitted lignified walls. 



4. Muehlenbeckia axillaris Walp. 



Growth-form. — '* A small much-branched prostrate or diffuse shrubby 

 plant, usually forming densely matted patches 3-12 in. diam., but sometimes 

 open and straggling ; stems and branches woody ; branchlets puberulous. 

 Leaves on rather long petioles, small, T ^y— -Jin. long, broadly oblong or 

 ovate-oblong or almost orbicular, obtuse or refuse, rounded at the base, 

 flat, quite glabrous, dotted beneath." 



Anatomy. 



Leaf. — The upper epidermis consists of large cells with thin walls, 

 except the external ones, which are slightly thicker. There is a very thin 

 cuticle. The epidermal cells form mucilage-sacs. The lower epidermis is 

 similar to the upper. A few stomates are found on the upper surface, but 

 they are much more numerous on the lower surface ; the guard-cells are 

 small and are level with the other epidermal cells. On both surfaces of the 

 leaf there are hydathodes, which are sunk in small depressions ; they are 

 more numerous on the lower than on the upper surface. 



The chlorenchyma is differentiated into palisade and spongy tissue 

 The palisade tissue is found on both surfaces of the leaf ; there are 3-4 

 layers of cells on each side. The cells are small, their walls are thin, and 

 they contain numerous small chloroplasts. The outer layers contain tannin. 

 The cells are closely packed, so that there are only very small intercellular 

 air-spaces. The spongy tissue consists of fairly large cells with thin walls 

 and containing numerous small chloroplasts. The air-spaces in this tissue 

 are larger, and some of the cells contain tannin. 



The vascular bundles are frequent, but of small size. Above the xylem 

 there is some stereome, and above this small-celled parenchyma. There 

 is also small-celled parenchyma below the phloem. Each vascular bundle is 

 surrounded by a sheath of large parenchymatous cells, which contain tannin. 



Stem. — The cork forms a fairly wide zone of very small compact cells. 



The cortex consists of oval cells which are closely packed together, so 

 that there are only very minute intercellular air-spaces. Most of the cells 

 contain tannin. 



The pericycle fibres form a narrow, more or less continuous band 1-2 

 cells wide. The cells are small, and have thick walls and small lumen. 

 The phloem forms a wide band, in which the parenchymatous cells contain 

 tannin. The xylem consists almost entirely of wood-fibres, but there are 

 a few vessels of large diameter. 



The medullary rays are multiseriate and are very wide. They consist 

 of small cells with thickened lignified walls, and they contain abundant 

 large starch-grains. 



The pith consists of rounded or polygonal cells with thick lignified walls. 

 They are closely packed together, and are full of large more or less poly- 

 gonal starch-grains, and some contain tannin. 



