]3ii{i,_ — Lianes of the Ancient Forest of Ganterhury Plains. 335 



the best conditions of growth — i.e., nearness to the underlying shrubs, from 

 which transition is easy, and abundance of supporting branches for the 

 climbing-organs. Branches of the liane may bridge the space between 

 adjacent trees, and the new support be utilized for further display of foliage. 

 Should this intervening space be small, it may be bridged by a single branch ; 

 but in many cases two or more projecting branches may intertwine and be 

 held in position by reciprocal grasping of their petioles. By the strength 

 thus attained these branches may reach a support at a distance of 1-5 m. 



AVhere low shrubs form the only support for the Clematis, the liane 

 grows horizontally along the tops of these shrubs. The action of the petioles 

 prevents the displacement of the stem by the wind, and ensures the main- 

 tenance of the leaves in the favourable positions they have taken up. The 

 primary arrangement of leaves is decussate, and in cases where the stem 

 stands erect this position is maintained ; but in stems growing along the 

 top of a shrub, and on stems which trail along the ground, there occurs 

 torsion of the stem, as a result of which the leaves lie in two rows. In 

 whatever position a leaf arises, the petiole twists so that the laminae of the 

 leaflets lie at right angles to the incident rays of light. 



From stems which are lying on the ground adventitious roots arise 

 where there is an abundance of moisture. These roots grow chiefly near 

 the surface of the ground, and often attain a considerable length. 



B. LEAF. 



(i.) Leaf -form. 



Leaves decussate, petiolate ; on adult plants 3-foliate, coriaceoiis, glossy, 

 upper surface dark green, under surface paler green ; leaflets 4-8 cm. long, 



-M^-^ 



Fig. 6. — Clematis indivisa. Variations in leaf-form. 



ovate-oblong or ovate-cordate ; margin entire or lobed. On juvenile ])l(^nts 

 the earliest leaves are simple, usually ovate-oblong or ovate-lanceolate, 

 3-5 cm. long ; in rare cases, linear-lanceolate, 7-10 cm. long ; subcoriaceous. 



