38 Transactions. 



(J.) Pimelea prostrata var. repens. 



This is not a true cushion-plant. P. prostrata has several varieties, ranging 

 from suberect to prostrate, but as the plant I am calling var. repens has many 

 characteristics in common with the true cushion-plants it is included here 

 and briefly considered. 



Its habitat is grades 2 and 3 and old terrace, but it is most abundant 

 on the latter. 



The growth-form is either a deep mat or a convex cushion (Plate V, 

 fig. 1). There is one main central root, from the top of which radiate 

 manjr branches, which trail horizontally over the shingle, and give off 

 many secondary branches terminating in lax branchlets. The stems are 

 woody, tough, and flexible. But few adventitious roots are given off from 

 forms growing on a shingly substratum, though forms on the old terrace 

 root copiously. 



The plant in question is undoubtedly the loosest of all the plants con- 

 sidered ; no filling-material exists. The main root (Plate V, fig. 2) is 

 usually very long — in one case as much as 60 cm. ; it penetrates more or 

 less vertically. The leaves are quadrifariously imbricated on the branchlets ; 

 elliptic -oblong, coriaceous ; length, 3 mm. During the winter anthocyan 

 is developed at the leaf-edges. On old terrace this plant assumes a more 

 spreading habit, with laxer stems and larger leaves. 



The long root (for the size of the plant), small coriaceous leaves, and 

 stunted form point to a plant adapted to a substratum where the water- 

 table is liable to fall considerably. As far as this paper is concerned, the 

 main point to note is the long tap-root and spreading (espalier) habit of 

 the branches. 



(K.) Muehlenbeckia axillaris and Acaena microphylla (in its widest sense).* 



These two forms hardly fall within the category of " cushion-plants " ; 

 they are mat-plants in the widest sense. Both are woody, Muehlenbeckia 

 most so. Both straggle unevenly over the surface of the shingle or hang 

 down over " banks " ; but as these two, especially Acaena, are among 

 the most plentiful of the plants on the river-bed it is admissible to treat of 

 them, however briefly. 



Muehlenbeckia axillaris occurs on all grades of terrace above the second. 

 It especially grows on the edges of the " banks " of the various terraces. 

 Plants were also found at an altitude of 1,000 m. The growth-form is 

 a loose mat of interwoven wiry branches sparsely covered with small leaves. 

 The mats vary in depth from 3 cm. to 4 cm., and are of all diameters up 

 to 50 cm. The leaves are more or less vertical, and to a certain extent 

 form the surface of the mat. 



The stems are wiry, tough, and black. The leaves are .small, ovate- 

 oblong, dark green, coriaceous, and about 4 mm. long. The roots are 

 tough and wiry, and are produced abundantly from the stem. The flowers 

 are dioecious. The fruit consists of a small black triangular nut, surrounded 

 by the lobes of the perianth, which becomes white and succulent. There 

 is no filling-material. In winter the leaves develop anthocyan. 



The succulent perianth should provide for distribution by birds, but 

 the writer observed no seedlings. The plant is propagated chiefly by 



* This is an aggregate species with two main divisions — perhaps species— which 

 even in the limited area dealt with contain numerous well-marked forms. 



