Spkiomt, Cockaynj;, Laixg. — Mount Arrowsmith District. 365 



trunk. Olcarin iUcijolia was noted as quite 12 m. tall, and its trunk 71 cm. 

 in diameter, a truly remarkable size for a tree composite. 



The behaviour of Gaya Lyallii within the forest is a matter of interest 

 which still requires a satisfactory explanation, our remarks below notwith- 

 standing. In none of the young plants examined, which grew upon the 

 forest-floor, was the main stem at first erect; on the contrary, it was 

 prostrate for many centimetres, putting down roots into the loose sub- 

 stratum. In nearly all the plants examined the apex of this creeping stem 

 was damaged, but it put forth erect branches which ultimately, as examina- 

 tion of many plants at different stages proved, became the final trunk. 

 Leaning trunks of Gaya put forth rapidly growing erect stems (suckers), 

 which would finally resemble trunks. How far the floor of moist loose 

 humus and semi-decayed leaves, which certainly would favour the pro- 

 duction of adventitious roots, which by their pull would hold the shoot to 

 the ground, is responsible for this primary creeping and rooting habit it is 

 hard to say. Other shrubs of this association show the sam.e pheno- 

 menon — e.g., Aristotelia fruticosa, " normally " a dense divaricating shrub, 

 an example of which was noted with the basal 4 cm. prostrate and rooting, 

 then the succeeding 5 cm. raised from the ground but still almost horizontal 

 and giving off two vertical branches, and finally 3-5 cm. bending upwards 

 until erect. The cases already cited by Cockayne (1908) of Styphelia fasci- 

 culata and Myrtus pedunculata, both " normally " erect shrubs, but on the 

 moist mossy floor of the subalpine forest of Ruapehu being creeping and 

 rooting plants, not erect at all, are analagous examples. 



The divaricating shrubs are not nearly so dense as in the open. Co- 

 prosma 'parviflora, for example, has in this forest several stems which are 

 quite without branches for the lower two-thirds, when they arch down- 

 wards and branch abundantly, this growth-form reminding one of the usual 

 mesophytic habit of C. joetidissima, plants generally quite dissimilar in form. 



The moss-clad horizontal trunks favour the presence of epiphytes, Senecio 

 elaeagnijolius especially following this manner of growth, and attaining 

 a remarkable size. As the plant increases in bulk the moss no longer 

 supplies enough water, and the roots lengthen, pass downward, and enter 

 the soil. Finally such roots may grow together and make a trunk. Many 

 of the trees of Griselinia littoralis and Oleana ilicifolia have also originated 

 in this manner. 



The two tall trees may both be considered xerophytes. Both can 

 tolerate physiologically dry stations — e.g., wet peaty soil ; but Podocarpus 

 Hallii — nor P. totara, for that matter — does not appear capable of enduring 

 a steppe climate, or, in other words, they are not found at present under 

 such xerophytic conditions as is Nothofagus cliff ortioides. So far as form, 

 leaf -structure, and so on, are concerned, there seems no reason why the 

 totaras should differ in their requirements from the beech. Certainly the 

 Nothofagus is more plastic ; it can more readily change its form accord- 

 ing to circumstances ; it is on the borderland of the deciduous habit ; 

 and as a forest it has wonderful powers of rejuvenescence, thanks to the 

 shade-tolerating power of its seedhngs. The above would give it an ad- 

 vantage over P. totara or P. Hallii, but in addition, as in many other 

 plants, there are physiological distinctions not recorded, or not yet esti- 

 mated, in form or structure which determine the habitat-range of a species. 



As for the totara forest of the Kakaia Valley as a whole, it is altogether 

 more mesophytic than is the N. cliff ortioides association, and must be classed 

 with rain forest. 



