Bird. — Lianea of the Ancient Forest of Canterbury Plains. 347 



rooting by creeping stems in moist positions. In M. hypericifolia the roots 

 arising from stems lying on the forest-floor are very numerous. Now, the 

 surface roots of the forest-trees are often semi-exposed, and covered to a 

 greater or less extent by debris and bryophytes, so that moisture-conditions 

 on these roots may not be very different from those in the surrounding 

 soil. If so, we should expect that if it is moisture which acts as a stimulus 

 to the formation of the adventitious roots, then the rooting of Metro- 

 sideros stems lying over these surface roots would be a natural occurrence. 

 And such is actually the case. It is probable that certain physiological 

 races would arise which required a smaller amount of moisture to stimulate 

 adventitious rooting, and so roots might be given off when stems were in 

 contact with the moist bases of tree-trunks. By secretions the roots might 

 easily be attached to the trunks, and thus the plants could raise themselves 

 from the forest-floor. Greater heights would be reached by the plants 

 whose tendency to rooting was greatest under the drier conditions which 

 would be met at the increasing distance from the forest-floor.* And even 

 now, as has been stated above, M. hypericifolia is found only in the most 

 shaded positions of the Riccarton Bush, and these plants do not attain 

 a very great height. But other species seem to thrive under drier con- 

 ditions. For example, the writer has observed in the Botanical Gardens 

 at Wellington a plant of M. scandens. This was growing in the open, and 

 formed a much-branched dense shrub about 50 cm. high. On one side, 

 however, a branch has come into contact with the stem of a shrub, and by 

 means of its climbing-roots it has ascended this stem to a height of 1 m. 



3. TWINING-PLANTS. 



When we turn to twining we are dealing with a phenomenon which is 

 of frequent occurrence in plants, and it is found not onlv in those which 

 can at once be classed as true lianes, but also in others in which the 

 twining is perhaps only slightly marked. It is these latter which are of 

 importance in trying to trace the development of twining. 



The fern Pteridium esculentmn (Forst. f.) Cockayne, which usually grows 

 in exposed stations, becomes in the shade a scrambler with elongated 

 stems, which sometimes show a slight tendency to twine. " So, too, 

 with the scrambling liane Lycopodium volubile Forst. f., which, gaining a 

 thin support, winds freely, the winding being in this case an hereditary 

 characteristic " (Cockayne, 1912, p. 21). 



An interesting case, not hitherto reported, is that of Carmichaelia 

 siihdata T. Kirk, which in the open is a rigid erect xerophytic leafless 

 shrub 0-5-1 m. high ; but it has been found by the writer in the shade as 

 a prostrate plant, with its stems hanging down over the edge of a rock 

 and showing a marked tendency to twine round one another. From this 

 plant a shoot rose upright for about 50 cm. Towards the distal end it 

 was twisted and coiled into a spiral, giving the appearance of a " searcher 

 shoot " of Muehlenbeckia australis which has commenced its spiral growth. 

 Unfortunately, no opportunity arose of visiting this remarkable plant later 

 to note the further growth of the shoot. The discovery of this plant seems 

 to be of considerable importance. Climbing is not unlmown in the genus 

 Carmichaelia : it is hereditary in C. gracilis, a rare scrambling liane growing 



* It must be remembered that the tree-trunks are kept comparatively moist by the 

 dripping of water during atmospheric precipitations. 



