Foweraker. — Mat -plants and Cushion-plants of Cass River Bed. 3 



a mat-plant, but the vertical branches are longer, so that the whole growth 

 is deeper and tends to assume a hemispherical form. 



All the types considered consist, in their early stages, of a long vertical 

 tap-root, crowned by a disc of horizontally-spread radial branches closely 

 appressed to the soil. At first no adventitious roots are produced by these 

 branches, but in many types these appear later. The horizontal stems 

 branch frequently, so as to produce a mass of stems forming a mat or disc, 

 with the primary tap-root in the centre. Many vertical branches are given 

 of! from these horizontal stems, and it is chiefly these vertical branches 

 that are clothed with the leaves, which are small. The ultimate branches 

 are compacted together in varying degrees of closeness, and this compact- 

 ness determines the density of the mat or cushion. These ultimate branches 

 will be termed for brevity " branchlets." Each branchlet is clothed with 

 leaves, which are always small and frequently closely appressed to the main 

 axis. The leaves die away towards the proximal portion of the branchlet. 

 The distal end of the branchlet terminates in a bud, below which are several 

 more or less expanded leaves with a close spiral phyllotaxy. This grouping 

 of the terminal bud and leaves makes the end of the branchlet, when viewed 

 from above, appear as a rosette. This term " rosette " will be used to 

 denote the distal leafy portion of the branchlet. It will be easily seen that 

 the rosettes form the " surface " (" Flache," Schroter and Hauri) of the 

 cushion, and the more compact and equal in length are the branchlets the 

 more even will be the surface. Neglecting the character of the surface, 

 the cushion itself may not present a flat or evenly convex exterior, but 

 may, owing to the unevenness of its substratum, be thrown into various 

 mounds and hollows. This will constitute the " contour " of the cushion. 



Lastly, as the leaves die away on the branches, and as sand, silt, and 

 other debris are blown or washed upon and into the cushion, the central 

 portion of it — i.e., the spaces between the main stems, branches, and 

 branchlets — becomes filled with a kind of humus. This will be referred to 

 as " filling-material " (" Fullmaterial," Schroter and Hauri). It plays a 

 most important role in the economy of many cushions. 



(C.) List of Species dealt with. 

 (a.) Cushion-plants : — 



1. Raoulia lutescens (T. Kirk) Beauverd. (Compositae.) 



2. Raoidia Haastii Hook. f. (Compositae.) 



3. Scleranthus hiflorus (Forst.) Hook. f. var. (Caryophyllaceae.) 



(6.) Mat-plants : — 



4. Raoulia tenuicaulis Hook. f. (Compositae.) 



5. Raoidia australis Hook. f. : several distinct forms. (Compositae.) 



6. Raoulia glabra Hook. f. (Compositae.) 



7. Raoulia subsericea Hook. f. (Compositae.) 



8. Raoulia Monroi Hook. f. (Compositae.) 



9. Acaena microphylla Hook, f., in a wide sense. (Rosaceae.) 



10. Coprosma Petriei Cheesem. : two varieties. (Rubiaceae.) 



11. Muehlenbechia axillaris Hook. f. (Polygonaceae.) 



12. Pimelea prostrata (Forst. f.) Willd. var. repens Cheesem.* (Thy- 



melaeaceae.) 



* Whether the plant here dealt with is really var. repens Cheesem. the writer does 

 not know. Cheeseman (1906, p. 613) gives no localities for any of his three varieties. 

 Var. repens is evidently identical with Hooker's var. £, which he states is " abundant, 

 especially in hilly districts " (Handbook of the New Zealand Flora, Part I, 1864, p. 244), 

 which distribution fits in admirably with the Cass plant. 



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