Bird. — Lianes of the Ancient Forest of Canterhury Plains. 327 



seem to be shade and moisture. Eoot-hairs are usually absent from the 

 anchoring-roots, but in a moist chamber they arise in large numbers. If 

 the roots fail to come in contact with a support they become attenuated, 

 and remain unbranched, but in other cases they branch freely and grow 

 to a length of 3-4 cm. In more exposed situations the plants thus gro\ving 

 along taxad-roots do not elongate very much, but tend to become more 

 bushy. The leafy branches are very numerous, and by their interweaving 

 support each other, so that the plants form small leafy clumps up to 40 cm. 

 in height. 



B. LEAF. 



(i.) Leaf-form. 



Leaves distichous, glabrous, subcoriaceous, sessile or subsessile, 0-8- 

 1-5 cm. long, ovate-oblong or ovate-lanceolate; acute, apiculate, or obtuse. 



(ii.) Leaf -anatomy. 



{a.) Shade Leaf. — Epidermis : Cells in transverse section of leaf iso- 

 diametrical ; outer walls slightly thickened. Stomata : Lower surface only ; 

 slightly raised above level of epidermal cells. Chlorenchyma : Palisade — • 

 Usually 3 layers cells, elongated, but not closely packed. Spongy — Cells 

 roundish or irregular ; intercellular spaces very large ; tissue comprises 

 two-thirds of leaf-thickness. Vascular bundle : Surrounded by a sheath of 

 thick- walled stereome, 1-2 layers thick. Calcium oxalate : In chlorenchyma 

 in aggregate crystals. Secretory cavities occur beneath the epidermis, and 

 are lined by a distinct epithelium ; they are described by Solereder 

 (1908, p. 3-53) as schizogenous in origin ; more abundant on upper surface. 

 Leaf-margin : Epidermal cells are here larger, and have thicker walls. 



(6.) Sun Leaf.- — -Epidermis: Cell- walls thicker. Stomata level, with 

 epidermal cells ; ratio of palisade to spongy tissue is greater than in shade 

 leaves. Palisade cells are more closely packed, and intercellular spaces 

 are smaller. 



(c.) Climbing-organ. — {{.) Climbing-roots: The vessels of the central 

 cylinder have small lumina and very thick walls. Endodermis forms a 

 distinct ring of large, thin-walled cells. Cortical cells in young roots contain 

 chloroplasts ; but in older roots the walls of the outer cells become lignified, 

 and the cells lose their contents, forming a strong peripheral band of 

 mechanical tissue. Root-hairs are absent, but can be indiiced by placing 

 the roots in a moist chamber. 



(ii.) Absorbing-roots : The vessels have slightly larger lumina, and the 

 cortical cells continue their functions, this resulting in the absence of peri- 

 pheral mechanical tissue. This distribution of mechanical tissue is in both 

 types of root advantageous for resisting the particular strains to which 

 the roots are exposed. Thus the anchoring-roots must resist vertical 

 strains, due to the weight of the plant, and lateral strains, due to the action 

 of the wind and to growth in circumference of the support. In the absence 

 of peripheral mechanical tissue the roots would be subject to injurious 

 torsion ; and, further, the tissue prevents injury to the living cells through 

 crushing or attrition ; but in the absorbing - roots the axile arrangement 

 of mechanical tissue is the more advantageous, for they have to withstand 

 pulls from various directions, and by the axile arrangement of mechanical 

 tissue the stress is most evenly distributed. 



