Foweraker. — Mat-plants anil Cushion-plants of Cass River Bed. 37 



clothed with distant short white bristly hairs. The whole leaf is slightly 

 incurved ; its average position is vertical. There is no great difference 

 between the marginal leaves and those nearer the centre of the mat. 



This is the first of the types considered where the rosette ceases to 

 become conspicuous. The branchlets are short, and bear from two to six 

 leaves, which stand out stiffly, and do not form a distinct rosette. 



A transverse section of a leaf shows the following anatomical structure : — 

 Cuticle thick. Stomata on both surfaces, level with surface of cuticle. 

 Hairs arising from a single epidermal cell, unicellular, short, tapering 

 bluntly, slightly curved, shaped like a cow's horn, and covered with minute 

 papillae. Mesophyll : Palisade three layers, upper two fairly regular and 

 closely packed ; upper layer has red anthocyan in winter ; the palisade 

 occupies approximately half the thickness of the leaf. Spongy tissue of 

 rounded cells, rather closely packed for aerenchyma ; air-spaces not large 

 or numerous. Oil-globules plentiful ; a large one occurs in each cell of 

 mesophyll. Crystals abundant. Chloroplasts small and numerous. 



(c.)- Root. — In old mats it is difficult to distinguish any main root, 

 because a mass of adventitious roots spring from the lower surfaces of the 

 creeping stems. The larger roots are tough and woody, have large vessels, 

 and show an internal structure much the same as the stem. 



(d.) Flower and Fruit. — Coprosma Petriei, like the other members of the 

 genus, is dioecious. The flowers are solitary, terminating the branchlets. 

 The corolla is inconspicuous, a purplish grey, funnel-shaped, four-lobed, 

 and about 8 mm. long. The female flowers have a minute four-toothed 

 calyx, but this fs wanting in the males. There are usually four exserted 

 stamens, with long filaments, and large anthers, producing copious dry 

 pollen. Styles two, long, papillose, sticky. Fruit an ovoid drupe, very 

 succulent, containing two one-seeded plano-convex pyrenes. The red or 

 •.Mvenish drupes are very attractive to birds, which are the agents of dis- 

 tribution for this species, as evidenced by bird-droppings containing masses 

 of C. Petriei pyrenes. 



fy.) Relation to other Plants. 



Seldom does this species occur as a " pure " mat, but is usually inter- 

 mingled with other plants. Only on the " banks " of the old terrace are 

 "" pure " mats found. On old terrace one mat, having an area of 1 square 

 metre, had the following plants mingled with it : Festuca novae-zealandiae, 

 Discaria toumatou, Raoulia subsericea, Hijpochoeris radicata, Holcus lanatus, 

 Geranium sessiliflorum var. glabrum, Rurdex Acetosella, Gnaphalium collinum, 

 M "ehlenbeckia axillaris, Styphelia Fiaseri, Cerastium glomeratum. 



(o.) Conclusions. 



This species, like the previous ones, shows complete adaptation to its 

 environment. Its mat-form, its woody stems and tough roots, and the 

 xerophytic nature of its leaves are all in harmony with its surroundings. 

 The copious production of dry pollen, the pendulous papillate glutinous 

 styles, and the small inconspicuous flowers point to wind-pollination ; and, 

 as wind is only too much in evidence in the Cass Valley, this means of 

 pollination should be very efficient. Distribution of the seed by birds is 

 well provided for. Another xerophytic character in common with the 

 raoulias is the conspicuous endodermis. The oil in the mesophyll cells 

 deserves notice, and may be perhaps explained by Haberlandt's suggestion 

 of its providing a screening vapour (1914, p. 515). 



