YOUNG TREES AS EPIPHYTES. 57 
flaccidum), the shining-spleenwort (Asplenium adiantoides), many of 
the filmy ferns, and the pendulous club-moss (Lycopodiwm Billardiert). 
Seedling trees are very common as perching-plants, or epiphytes, 
to use the scientific term, and some of the forest giants begin their 
career in this manner. ‘These finally send down to the ground roots 
which grow into a solid “ root-trunk”’; the former host is locked 
in their embrace and stifled. The northern rata (Metrosideros 
robusta), the Chatham tree-heath (Dracophyllum arboreum), and in 
the southern parts of New Zealand the broadleaf (Griselinca littoralis) 
frequently behave in this most ungrateful manner (fig. 30). So, 
too, the puka (G. lucida) may behave similarly, though such is not 
its usual custom. With regard to the northern rata (Metrosideros 
robusta), the popular but erroneous belief is that the descending roots 
are ascending climbing stems, and that these eventually grow together 
and stifle the tree. This error has arisen through mistaking the 
climbing stems of the scarlet climbing-rata (M. jlorida) for the 
descending roots of the northern rata (1. robusta). 
Though many plants are “eager” to get into the fresh air and 
sunlight, others are the reverse, and have developed different adapta- 
tions which enable them to lead their special life. The interior of 
a thick forest has an atmosphere charged with vapour not altogether 
unlike that of a glasshouse. Plants living under such conditions are 
subject to much the same environment as submerged water-plants, 
and have developed similar leaves, which are quite thin and able 
to absorb any water which may fall upon their surfaces. Such, 
amongst others, are the filmy ferns (species of Hymenophyllum and 
Trichomanes), the beautiful crape-fern (Leptopteris superba), and its 
relative the single crape-fern (Leptopteris hymenophylloides). Plants 
like these can exist only in a moist atmosphere ; the full rays of 
the sun or a dry atmosphere cause them to shrivel up, and they 
soon die when removed from their forest home. Many mosses and 
liverworts also belong to this category, and mimic in their forms 
the smaller ferns, to which, of course, they bear no relationship. 
Although possessing much thicker leaves than those of the filmy ferns, 
the black hard-fern (Blechnum nigrum) is confined to the moistest, 
most shady parts of the forest, and is never found under other cir- 
cumstances. It may be pointed out here that leaves of ordinary 
trees and shrubs are more or less impervious to water, and, as a rule, 
the more drought-resisting the plant, the more impervious the leaf. 
