Fowerakeb. — Mat-plants and Cushion-plants of Cass- River Bed. 35 



crystals are very large in proportion to the size of the midrib — in some 

 cases they are half the size of the cross-section of central vein. Vascular 

 bundle : Sheath very distinct, of large, clear, ovoid cells. Stereome : Two- 

 thirds of the bundle consists of a rod of stereome below the phloem. 

 Phloem of small parenchymatous cells and sieve-tubes. Xylem apparently 

 weak ; the large central bundle has five to ten vessels, between which is 

 xylem parenchyma. Smaller bundles occur above the main one, but possess 

 no stereome. 



(c.) Root. — The tap-root is long, often attaining 30 cm. in shingly sub- 

 strata. On old terrace it is much shorter. It is pale straw-colour, flexible 

 like rubber, and has an internal anatomy very much like the adult stem. 

 In deep cushions with much filling-material adventitious roots are given 

 off into the interior. 



(d.) Flower and Fruit. — The flowers were not observed, but Cheeseman 

 (1906) describes them thus : " Flowers minute, in pairs, or more rarely 

 solitary at the top of the peduncle, sessile within four minute concave bracts 

 placed crosswise. Perianth 4-lobed. Stamen one, inserted on an annular 

 membrane near the mouth of the perianth. Fruiting perianth about y 1 ^ in. 

 long, hard, ovoid at the base ; lobes erect. Utricle membranous, included." 



The fruit is a membranous utricle enclosed in the persistent and hardened 

 perianth. Seed lenticular, smooth. The fruits easily break off, and many 

 fall on the surface of the cushion. 



(y.) Epharmonic Variations. 



There are two growth-forms, as stated above — one a cushion with tap- 

 root only, and the other almost a mat with adventitious rootlets. The 

 habitats of these two forms have been already given. Greenhouse cultures 

 produce a lax growth, which, save for the decussate phyllotaxy, much 

 resembles that of Raoulia tenuicaulis. 



(8.) Conclusions. 



The outstanding feature of this plant is its xerophytic character. Its 

 long flexible tap-root — very obvious in pure river-bed forms — enables it 

 to exist among shingle when the water-table has been much lowered. Its 

 thick sheath of cellulose-thickened pericycle serves as a protective pad 

 against the crushing effects of moving shingle. 



Its stems, which in the young stage have a well-marked endodermis, 

 in adult forms have a coating of cork and cellulose. This shuts off con- 

 nection between the central conducting cylinder and the exterior, and allows 

 of maximum efficiency in water transport. The leaves show many xero- 

 phytic features — subulate erect form, thick cuticle, stereome-strand. On the 

 other hand, their chlorenchyma is not closely packed, and water-tissue is 

 absent. 



Lastly, one of the growth-forms of the plant- — a nearly hemispherical 

 cushion — is a common xerophytic character. 



(I.) Coprosma Petriei. 

 (".) Habitat. 



Coprosma Petriei is confined to old terrace (terrace proper). It occurs 

 on all portions of the terrace, and on the lower slopes of the bordering 

 lulls, especially on consolidated " shingle-fans." It grows densest, however, 

 2* 



