346 Transactions. 



it is generally agreed that the chief factors determining stem- elongation 

 are moisture and diminished light, and thus the variation in the life-form 

 of Fuchsia Colensoi can be readily understood. This species, tvhich forms a 

 compact, much-branched shrub in the open, in the forest-shade has stems 

 which are greatly elongated and tvhich have few lateral branches. These 

 stems can rapidly push their way into vegetation above them, and by 

 leaning against supports attain a height of fully 4 m. 



That this scrambling habit was at first the effect of environmental 

 stimuli — moisture and shade- — ^cannot, in the face of the behaviour of other 

 plants in similar conditions, be doubted ; and it is possible that races were 

 evolved in which the scrambling habit became hereditary. On this point 

 L. Cockayne (1912, p. 21) says, "It is possible that there may be climbing 

 and non-climbing races. This is the more likely as the ' species ' is con- 

 sidered variable, and large forms are said to ' almost pass into F. excorti- 

 cata ' (Cheeseman, 1906, p. 187), which is a small tree or shrub, but never 

 a liane." Such a view receives support from the very great elongation of 

 stems of F. Colensoi in positions in the forest where supports are abundant 

 —positions where the stems often lie along the ground for fully 5 m. 



When species of Rubus and other plants possessing prickles commenced 

 growth in the forest-interior they would, on account of their prickles, be 

 better suited for reaching the light than would plants without such append- 

 ages.* They would thus be able to propagate their kind more quickly, 

 and, with their larger number of descendants, races in which the scrambling 

 habit was hereditary might soon arise. And in comparing the relative 

 abundance of Rubus plants in the forest, and the luxuriant growth of the 

 plants there, with those in more open situations, it seems probable that 

 natural selection would by itself result in the climbing habit being retained. 

 In fact, it seems that in the species of Rvbus found in the Riccai-ton Bush the 

 scrambling habit is in all cases hereditary, for those plants which grow in 

 the open do not form shrubs, but low straggling masses, which resemble 

 somewhat the exposed forms of more specialized lianes. In the forest- 

 scramblers the importance of leaves in climbing has been pointed out 

 above, and so it is interesting to note hoiv in one of the species of Rubus, 

 R. cissoides, the leaf has changed its role, or, rather, has acquired a new role, 

 being now a special climbing-organ. 



2. Root-climbers. 



In this class of climbers the small number of representatives studied by 

 the writer makes it difiicult, using only the facts derived from the Riccarton 

 Bush, to conceive means by which the climbing habit has been gradually 

 adopted, but the variations in the life-form of Metrosideros hypericifolia 

 may have some bearing on the question. In this species it is evident that 

 there is no sharp distinction between climbing-roots and absorbing-roots. 

 Both are at first similar in structure ; and it seems probable that the nature 

 of the environment determines whether the roots shall elongate and act as 

 absorbing-organs, or whether they shall remain comparatively small and 

 fasten the liane to the support. 



It will be noticed from accounts of the life-form of the lianes that in all 

 the species the important fact stands out that there is a tendency to adventitious 



* Before the scrambling growth was commenced, however, the prickles would 

 possibly be of no use to the plants possessing them. 



