16 Transactions. 



hairy and consequently greener leaves. Indeed, the branchlets under these 

 conditions resemble the hairy greyish forms of R. tenuicaulis, but can be 

 distinguished from these by the leaf-apices, which are not apiculate, and by 

 the thicker lamina. 



(8.) Conclusions. 



This plant may be ranked with R. tenuicaulis as a denizen of the open 

 shingle, but its much more xerophytic nature, as shown by its small, thick, 

 hairy leaves, and its rigid stem-structure allows it to exist longer than the 

 latter on the ascending grades of terrace. Its copious seed-production and 

 the long pappus-hairs permit of rapid seed-dispersal. 



, . „ (C.) Rao alia lutescens* 



(a.) Habitat. 



R. lutescens is a plant of definitely restricted habitat. It occurs only 

 on transition-terrace grades 2 and 3. Its comparative slowness of growth 

 prevents its gaining an early footing on the lower grades, and before the 

 grades on which it grows pass into the highest stages it dies out. Essentially 

 a plant of open shingle where the plant-covering is widely scattered, it dies 

 away when encroached upon by other plants. Careful search of the old 

 terrace revealed no trace of this plant save at the margins where the change 

 to the lower grades began. 



It frequently occurs on the edges of the terraces of intermediate grade, 

 where these form a " bank " to a stream or an old watercourse. The 

 cushions curve over the edge, forming a thick bulging " beading," and, 

 where the bank is deeply undermined, assist in holding the soil together. 

 The growth in such situations is very compact, and will easily bear the 

 weight of one's body on the edge ; whereas on portions of the undermined 

 bank where no such growth exists the slightest pressure will cause the 

 edge to fall down. R. tenuicaulis grows in similar situations on the lower 

 grades, but has not so great a consolidating effect. (Cf. Plate III, fig. 2.) 



((3.) Life-form. 



(1.) General. — -Next to Raoulia Haastii this species ranks as a true 

 cushion-plant. It is the most even and the most uniform of all the raoulias 

 dealt with in this paper. The cushions are more or less circular or elliptical 

 raised in the centre and gently sloping away to the margins. Geometrically 

 speaking, the cushion tends to take the form of the minor segment of a 

 sphere. (Plate IV, fig. 1.) The general contour is smooth. The surface 

 is the smoothest of all raoulias. The margin is well defined, as there is 

 practically no difference between the branchlets, rosettes, and leaves of the 

 margin and those of the centre. The cushions are of various sizes, four 

 measurements being 20 cm. by 15 cm., 40 cm. by 18 cm., 50 cm. by 50 cm., 

 100 cm. by 100 cm. A section through the cushion shows a layer-formation 

 due to the successive growth of branchlets, and it is possible that each 

 layer represents a season's growth (fig. 5). Some branchlets do not branch 

 at the tips to produce the ultimate ones of the new growth, but remain 

 short at their old level, and thus help to fill up the spaces between the stems. 



* The plant referred to in this paper as Raoulia lutescens is described in Cheeseman 

 (1906) as a variety of R. australis ; but Beauverd (1910, p. 221) rightly considers the 

 divergence between the two is enough to constitute a specific difference. 



