330 Transactions. 



below midrib ; one row of spherical thick-walled cells. Chlorenchyma : 

 Palisade — 3 layers of elongated cells arranged in vertical rows ; tissue 

 comprises one-half of leaf-thickness. Spongy cells nearly spherical ; inter- 

 cellular spaces small. Leaf - margin : Epidermal walls thicker than in 

 shade ; chlorenchyma cells more closely packed, and showing tendency 

 to elongate as in palisade tissue. Vascular bundle : One layered parenchy- 

 matous sheath. Calcium oxalate : Crystals in upper spongy tissue. 



5. MUEHLENBECKIA COMPLEXA. 

 A. LIFE-FORM. 



The members of this species are confined to the outer portions of the 

 forest, where the plants receive a large amount of light ; they are much 

 branched and of comparatively low growth. The species is most abundant 

 in the drier, well-drained soil. The climbing-stems — at most 2 cm. in 

 diameter — are covered with a rough blackish bark and trail along the forest- 

 floor for many metres, rooting freely at the nodes. When they reach any 

 thin stem they twine round it, and, as in M. australis, the twining is either 

 sinistrorse or dextrorse, the former being the more common, and, likewise, 

 any stem may change its direction of twining. The twisting of adult stems, 

 as well as the position of the lianes in relation to their supports, show how 

 former supports have been strangled ; but these occurrences are not so 

 well marked as in M. australis. This is due partly to the small growth of 

 M. complexa, which nowhere rises higher than 9 m., and partly to the nature 

 of the supporting trees and shrubs. These, as above mentioned, are much 

 branched, and often form dense masses of the divaricating life-form. In 

 reaching to the tops of these plants the liane shows a tendency to scramble rather 

 than to twine, interlacing branches being more favourable for scramblers than 

 for twiners ; but, although twining by M. complexa is by no means common 

 in such places, the twining, when it does occur, prevents the liane from 

 slipping from the support. In the light, at the edge of the support the stems 

 branch freely, and the lateral branches bear large numbers of leaves, which, 

 with the stems, form compact masses. These stems, although very slender, 

 arise in large numbers, and their tendency to twine round each other is 

 marked. By mutual support they may thus project for nearly 1 m., and 

 by so doing come into contact with new supports, which soon become 

 covered by the dense masses of liane-stems. These are greatest on the 

 tops of the supports, where they grow so close that no light can penetrate 

 the doise mass. Such masses are especially characteristic of the plants 

 of the forest-margin. Here the only supports are shrubs, which vary in 

 height up to 3 m. On these the lianes form masses which by their weight 

 bend the shrub down to the ground. They continue their branching, and 

 the intertwining branches soon obscure the support from view, the whole 

 mass then resembling a rounded cushion, often from 1 m. to 2 m. high, and 

 from to 2 m. to 4 m. across. 



B. LEAF.* 



(i.) LeaJ-form. 



Leaves alternate, petiolate, varying in shape and size, 0-5-1 -5 cm. long,, 

 orbicular or obovate, rounded or obtuse at tip, borne singly or in pairs 



* Like all the descriptions in this paper, this refers to the Riccarton Bush plant 

 alone, Were the " species " being dealt with for the whole of its area of distribution,, 

 the differences in leaf -form would be much greater. 



