HorLowaAv.—Studies in the New Zealand Hymenophyllaceae. 607 
characteristically confined to the under-side of inclined trunks and large 
boughs, and they grow generally in close colonies. It is obvious that the 
thread-like stems of these species could not carry an adequate water-supply 
from the substratum even if this were available. On the other hand, there 
is a very large extent of lamina in proportion to the size of the frond, this 
being especially the case in H. rarum; while in Н. Malingii, as has been 
noted, there is a very remarkable and eflective frond-modification for the 
purpose of frond absorption. H. ferrugineum is also invariably pendulous 
with overlapping fronds in its station on tree-fern stems, and the rhizome 
and stipe is slender, though not so much so as in the three above-mentioned 
species. 
: It is significant that these four species, which are thus so dependent upon 
frond absorption, show withering in times of drought to a markedly less 
degree than do other epiphytic species. In the case of H. Malingii the nature 
of the frond-tissues readily explains this. It has been suggested that the 
peculiar colour of the fronds of H. rarum and H. flabellatum may possibly 
serve to mask the cell-protoplasm from excessive transpiration. H. ferru- 
gineum is one of the hairy species. Its fronds are almost rusty-brown in 
colour owing to the dense clothing of stellate hairs on the margins of the 
segments and on the costae on both surfaces of the frond (see Plate 76). 
a single otherwise unaltered marginal cell. Whether the hairs in this case 
hindering transpiration through the overlapping of the fronds and also in 
holding water and humus against the roots. The stipe of T. humile and 
