326 Transactions. 



to curve was so great that they were practically encircling supporting 

 twigs to which they had become attached. It may, therefore, he said that 

 in this species the leaf has changed its function, and has become a distinct 

 climbing-organ. 



Not only are the leaf-prickles of importance to the plants in climbing, 

 but the stem-prickles, which persist for a great length of time, function 

 to some extent in this regard. They are practically absent from the stems 

 of R. cissoides, and it is interesting to note this absence going hand-in-hand 

 with the great development on the leaf-midribs of that species. In R. schmide- 

 lioides a few prickles are present. In R. australis they are more numerous, 

 and in R. subpauperatus they are very abundant. On stems of the last- 

 named species 1 cm. in diameter, many of the prickles can individually 

 withstand a strain of 900 grams. The average for the species is about 

 650 grams, and in the other species this same strain is the maximum which 

 they can withstand. 



3. Metrosideros hypericifolia. 

 a. life-form. 



This sjjecies is by no means common in the Riccarton Bush, there being 

 only about six individuals. These are confined to the damp shaded portions 

 of the interior, where they grow on the trunks of large trees to a height of 

 10 m. The stems are 3-4 cm. in diameter, and at about 3 m. from the ground 

 they usually give off numerous branches, whose growth is often more or less 

 erect, but which may be inclined to varying degrees. These branch again, 

 so that the whole plant forms a mat^-like growth round the support. Leaves 

 borne on these branches are arranged in two lateral rows ; though small, 

 they are in large numbers, forming a dense mass of foliage. When brightly 

 illuminated the branches hug the support, against which the leaves are 

 closely pressed ; but in shaded places growth is more vigorous, and branches 

 may project from the support for 50 cm., and by their interweaving form 

 dense masses. Usually the climbing-roots at the basal portions of the liane 

 are dead, and the stem swings freely. Branches which arise near the groimd 

 often grow out over semi-exposed surface roots, and finally on to the sur- 

 rounding forest-floor, where they become covered with debris and bear 

 roots which penetrate the soil for a depth of 10-12 cm. From these stems 

 leafy branches may arise erect for a few centimetres, or, as is more common, 

 they lie along the ground-surface. 



These surface-growing shoots are mostly foxmd in contact with the roots 

 of the kahikatea, which extend along the surface of the ground for many 

 metres. The main shoots of the liane keep in contact with the roots, while 

 lateral shoots branching ofi usually grow over the forest-floor, giving off 

 absorbing-roots. The stems which thus grow along the taxad-roots are 

 often broken by animals and other means, but the severed portions con- 

 tinue their growth, thus showing the efficiency of the absorbing-roots.* The 

 anchoring-roots which attach the liane to the support are usually dia- 

 geotropic, but it is evident that contact with the support may overcome 

 the influence of gravity. The factors influencing the development of roots 



♦Cockayne, L. (1909a, p. 14), describes how in the forest of Stewart Island there 

 is often a stout creeping stem beneath the loose peaty soil many yards in length, from 

 which climbing shoots may be given off, "the plants of adjacent trees in this manner 

 being at times merely branches of one plant." 



