Bird. — Lianes of the Ancient Forest of Cdnterhury Plains. 349 



4. Tendril-climbers. 



Tlie evolution of tendril-climbers has been referred to by Darwin, who 

 states, " With "respect to the sensitiveness of the foot-stalks of the leaves 

 and flowers, and of tendrils, nearly the same remarks are applicable as in 

 the case of the revolving movements of twining-plants. As a vast number 

 of species, belonging to widely distinct groups, are endowed with this kind 

 of sensitiveness, it ought to be found in a nascent condition in many plants 

 which have not become climbers" (1878, p. 197). 



In support of this statement is a series of plants explained by Miiller 

 (Journ. Linn. Soc, vol. ix, p. 344) — plants which represent stages from those 

 which climb by obtaining support from their branches stretched out at right 

 angles, such as Chiococca, to those whose branches form true tendrils, as 

 with StrycJinos. 



Transitions from leaf to tendril are also common, and so it is interesting 

 to note the behaviour of many leaves of Riibiis cissoides. As stated 

 ou p. 326, the leaves of this species are often reduced to midribs, which, 

 with their strong recurved hooks, form distinct climbing-organs. Manv 

 of the midribs are much curved at the distal end (Plate XXIII), and 

 in a few cases the midribs had actually encircled a twig with which they 

 had come into contact. It may therefore rightly be asked whether such 

 behaviour denotes the inception of tendril-formation. The plants possess- 

 ing the peculiarity have a marked advantage in gaining supports, so we 

 should expect that natural selection will preserve these plants, and that the 

 " rudimentary tendrils " will by this means be gradually perfected. 



V. GENERAL CONCLUSIONS. 



The descriptions given above of the life-forms of the lianes dealt with show 

 to a certain extent how luxuriant is their growth. Moreover, this luxuriant 

 growth is common throughout aU the New Zealand forest, to which the 

 lianes are often said to give an appearance similar to that of tropical forests. 

 Undoubtedly there is a Malayan element in the New Zealand forest, so that 

 at first thought it might appear that the lianes were of tropical origin. 

 But this is by no means the case. It is not the great heat alone of a tropical 

 rain-forest that is the primary cause of the liane habit, but rather it is this 

 combined with the excessive moisture of the atmosphere. In New Zealand 

 the moisture is also great, and the climate is equable without extreme heat 

 and cold. This condition of affairs is probably responsible for the high 

 development of lianes in New Zealand, and this view is supported by the 

 remarkable fact that there are here a large number of climbing Myriaceae, 

 a family without lianes in the rest of the world.* 



The individual lianes studied exhibit many characters in common, of 

 which we may first note the tendency to form adventitious roots. The 

 formation of such roots is, of course, common with many plants, being most 



*Clieeseman (1914, pi. 50) offers as an objection to this theory, for which I am 

 not piiraarily responsible, the fact that Pol3Tiesiaii and Malayan species of Metrosideros 

 have not become lianes, although the climate they are exposed to is " even more humid 

 and equable." I possess no exact details as to the life-forms or the exact environment, 

 on which all deponds, of each of the nine (mostly New Caledonian) Malayan and Poly- 

 nesian species; but, unless some of these are shrubs, the lianoid form would not be 

 expected. On the other hand, in New Zealand M. scandens (and probably M. florida), 

 M. diffusa, and II. albiflora possess both shrub and lianoid forms. 



