8 Transactions. 



(2.) Filling -material. — The filling-material in the case of this plant is 

 very varied in quantity. In its usual condition R. tenuicaulis forms a .shallow 

 mat of branchlets, so short that there is a very little depth below the rosettes. 

 The black dead leaves clothe the branchlets below the rosette, and except 

 these leaves and a modicum of wind-blown sand there is no other filling- 

 matter. 



But, growing as this plant usually does on the lowest grades of the 

 terrace, it is frequently subjected to inundation, and when this occurs its 

 mat is liable to be covered wholly or partially with sand. The rapid 

 growth of this plant during the spring and summer soon counteracts the 

 effects of being sand-covered. Several large mats were noted which had 

 been completely covered with sand during a flood some time near the end 

 of August, but in the first week in September the majority of the rosettes 

 were vigorously uplifting themselves above the sand-level. Many old mats 

 were of considerable depth (relatively speaking for R. tenuicaulis), being 

 about 4 cm. deep. Such mats have a filling-material composed chiefly of 

 sand, but the whole has a blackish-brown appearance, due to the colour 

 of the stems and dead leaves. Most of the filling-sand is due to flood 

 deposits; very little is wind-blown. Sandy areas are not so frequent in 

 the Cass Valley as in that of the Waimakariri, consequently miniature 

 sandstorms, such as often occur in the latter, are almost entirely absent 

 at Cass. 



(3.) Coloration. — As regards coloration this plant is most variable. 

 Typical mats during the summer and early autumn are a bright sap-green. 

 The hairy forms have a greyish tint. During the winter the variety- of colours 

 is most remarkable. Very few of the plants are of a greenish tinge ; none 

 of them have the deep-green colour so evident in the spring; those that 

 do exhibit green are of a yellowish-green tint. 



Many of the plants are densely hairy during the winter, and this aids 

 in giving a general greyish colour. This appearance is aided by the lower 

 leaves dying away, and their greyish colour shows here and there between 

 the rosettes. The edges of the leaves are yellowish or brownish, and the 

 whole of the plant at this stage is a greenish grey (this is the case with that 

 form which is green in summer). The greyish form does not alter during 

 the winter, for the leaves and colour seem the same as at other seasons. 



In the upper part of the Lower Valley, where large areas are covered 

 with mats which run into one another, each plant is of a different colour, 

 so that the original individual mats can be distinguished. The colours are 

 most varied — pale yellow-green to a fawny brown, and various shades of a 

 pinkish grey ; really the colours are indescribable. During the winter the 

 colours are rich. On one "island," amid river-bed proper, having an area 

 of 15 square metres, the whole surface, save for large projecting boulders, 

 was covered with R. tenuicaulis. The separate mats had run into one another, 

 but their individual outlines could be made out owing to their colours- — 

 all shades from sap-green to chocolate-brown through various yellow-browns. 

 Also, the hairy variety showed all colours from a pinkish grey to a brownish 

 grey. 



(4.) Morphology. — (a.) Stem. — The main stems are prostrate, closely 

 appressed to the ground, and above give off secondary branches, but below 

 root copiously. They are wiry, thin (main stem 2 mm. diameter, ultimate 

 branchlets - 5mm. diameter), and brownish or blackish in colour. The 

 branchlets vary in length according to the amount of filling-material — e.g.. 

 0-5 cm. in shallow mats to 1-75 cm. where filling-material is considerable. 



