Foweraker. — Mat-plant s and Cushion-plants of Cass River Bed . 21 



hue is due to the blending of the green and red may be illustrated by mixing 

 two water-colours, sap-green and crimson-lake. By varying the proportions 

 suitably a reddish chocolate-brown colour, similar to that of R. Haastii, 

 may be obtained. 



A small cushion of R. Haastii was removed in March, 1915, from the 

 Cass Eiver bed. and planted in a pot in a greenhouse near the east coast, 

 at sea-level. When removed from the Cass it was bright green, and it 

 retained its green colour throughout the winter. Practically no anthocyan 

 whatever was formed. Careful examination showed a tinge of yellow at the 

 angles, and a faint brown at the extreme tips of the leaves- — an effect due 

 to the weak development of the anthocyan. 



(4.) Morphology. — (a.) Stem. — The stems are thin, wiry, brownish, and 

 much wrinkled. The lower ones are prostrate, but the finer branches are 

 more upright, the uppermost ones bearing the terminal branchlets. Koot- 

 lets are given off from most of the lower branches. The average diameter 

 of the upper branches is 1-5 mm. 



The branchlets vary in length from 0-5 cm. to 1 cm. ; their axes are 

 straight and radially disposed in relation to the hemispherical cushion ; 

 they are as closely compacted together as in R. lutescens, but the coherence 

 to each other is not so great as in the latter, this being due to the glabrous 

 and more coriaceous leaves, so that when they dry the outer boundaries of 

 the whole branchlet are rather smooth. Hence the branchlets do not inter- 

 lock and adhere together so firmly as in R. lutescens. They are of quite as 

 uniform a length as in R. lutescens, so that the general surface is as even 

 as in the latter species. 



Transverse sections of stems from the centre of the cushion show the 

 following structure : Epidermis apparent only in the younger stems, but 

 soon thrown off with the outer cortical layers. Cortex of rounded thick- 

 walled cells, early becoming suberized and empty. Endodermis very dis- 

 tinct, though not so thick-walled as in R. australis. Phloem a very thin 

 layer ; pericycle-fibres appear in the periphery. Cambium single layer. 

 Xylem ring of dense tissue ; closely packed tracheides and vessels. Pith 

 a narrow column, early becomes lignified. In the very old stem the only 

 external covering is a layer or two of the remaining suberized cortex-cells 

 outside the endodermis. 



(6.) Leaf (fig. 6). — The leaves are stiff and rigid, minute, 2 mm. long, 

 approximately triangular in form, with a broad, spathulate, deeply hollowed 

 base (1-25 mm. wide), which sheathes the stem and edges of the neighbouring 

 leaf-bases. It narrows rather abruptly into a short subulate tip, the real 

 " lamina," which is semicircular in section, the flat surface facing the axis 

 of the branchlet. The tip is slightly curved inwards. On the convex 

 surface on both sides there is a longitudinal depression, and the epidermis 

 at these areas usually gives off a small patch of short silky hairs. 



The rosettes are minute (diameter on a surface view 2-3 mm.). The 

 leaves do not tend to come to the same level as in R. lutescens, so that a 

 side view of the rosette shows an elliptical contour. The average number 

 of leaves visible from above is twelve. 



A cross-section of the leaf (fig. 7) shows the following structure : — 

 Epidermis : Small roundish cells, many of which contain anthocyan. 

 Cuticle very thick towards the tip of leaf, but thins out towards basal 

 sheath. Stomata on both surfaces of leaf, but mostly on the outer convex 

 surface ; sunk below cuticle-level. Mesophyll : Near tip a band of about 

 two layers of cylindrical chlorenchymatous cells surrounds leaf. Between 



