4'20 PLANTS OF NEW ZEALAND 



:uid sword-like. They are usually covered with a brown, 

 silvery, silky, hoary, gold-coloured, snowy, or buff tomentum, 

 whicli makes them extremely attractive in appearance. In 

 some cases, tlie midrib is also brightly coloured. Thus, in 

 drlmisia Tjrircrsii, the leaves and flower stems are covered 

 with A rich brown velvety coating of hairs ; the midrib is a 

 deep purjjle, and the sheath is covered with a silky, snow- 

 white tomentum. Several species are frequently to be found 

 m cultivation, in rockeries and alpine gardens. 



The leaves in most species are constructed so as to avoid 

 excessive loss of water by transpiration. For example, those 

 of C. coriacea are stiff' and leathery. The lower side is covered 

 with a thick silvery felt of liairs, which also covers the upper 

 sides of the young leaves. As they grow older, however, 

 the tomentum of the upper-side becomes woven into a thin 

 skin that lies close to the surface of the leaf. Underneath 

 tins pellicle, lies the two-layered epidermis used for water- 

 storage. The sheaths are covered with a loose felt, whose thin 

 walled hairs probably absorb the water that runs down to them 

 fronr the surface of the leaves. This may be of special value 

 to the plant when the ground is frozen in winter, and water 

 cannot reach it through the roots. According to Kirk, 

 shepherds use the tomentum of this plant for lamp-wicks. 



C. LyaUii is even more admirably adapted than C. coriacea 

 for an alpine habitat. Indeed, Diels considers the structure 

 (jf its leaf unique amongst dicotyledons. It has narrow 

 linear leaves, that might be readily ixiistaken for those of a 

 grass, and which Diels compares in structure to those of a. 

 steppe grass. True palisade cells are wanting, and are replaced 

 by a chlorophyll-bearmg parenchyma of small rounded cells, 

 similar to that found m the leaf of an iris or grass. It is 

 curious that this structure should have been adopted, in a plairt 

 of an order so widely divergent from the grasses, but many 

 C.(jmposites have leaves which externally resemble those of a 

 glass, though it would be very difficult, perhaps impossible, to 



