Hotitoway.—Studies in the New Zealand Hymenophyllaceae. 587 
been looked upon as the least-specialized members of the family. I may 
state briefly that from an examination of the sporeling plants of all three 
species I have found that the multi-layered Af epe is developed secondarily 
in the ontogeny and from the vein outw wards the margins. The 
first-formed frond in all three species is rn a ahr linear form with an 
unbranched vein. The lamina is one cell in thickness, except immediately 
adjoining the vein, where it is three-layered, the outer dorsal and ventral 
cell-layers extending over the vein. Sections of succeeding fronds of young 
sporelings show that the next stage toward the multi-layered condition is 
attained by the development of a second and inner layer of small cells 
overlying the vein Fp dorsally and ventrally, at the same time the two or 
three interior cells of the lamina laterally adjoining the vein increasing in 
ment of this zone results from indiscriminate periclinal and anticlinal 
divisions of the cells of both the outer and the inner layers of the lamina, 
so that in progressively older fronds both its gradual outward extension 
towards the margin and also the further increase in width of the inner layer 
of the lamina in the same direction can clearly be traced. In these young 
sporeling plants, and even to a much later stage in their development, there 
is a broad zone of lamina extending inwards from the margin which remains 
in the original one-layered condition, and the irregular edge of the multi- 
layered portion of the lamina where it adjoins the outer one-layered portion 
can easily be seen by the naked eye. In all three species the cells of the 
inner layer of the lamina are comparatively pha and probably function 
as a water-reservoir. In young sporelings of T. renifor medi older 
frosts show a repeated forking of the vein A of the lamina that the 
_ young frond becomes somewhat digitate in form. The lamina soon extends 
and webs the segments together, although the margin of still older fronds 
remains more or less crenate. The lamina of the adult composite frond 
of this species is multi-layered to the margin, but whereas it is five cells 
thick in the oldest basal parts of the frond, it becomes four and finally only 
three cells thick towards the margin. It must be added that in well- 
grown plants all new fronds are reniform from the first. 
In the case of H. scabrum the multi-layered condition is attained much 
later than in the two other species, appearing first in the oldest parts of 
- аери frond. In this species the segments of the mature fronds 
wings of the rhachis permanently remain one cell in thickness for 
— pe in from the margins. 
to be noted in this connection that in the case of T. elongatum, 
in which species also the frond-lamina is particularly extensive, the lamina 
is two or three cells in thickness in those parts of the pinnae where the 
larger veins converge, but only in the immediate vicinity of the veins—z.e., 
the multi-layered condition does not extend чуеш very far towards the 
margins. innules of H. demissum show a circle of parenchyma one 
cell thick completely surrounding the veins, but in puel of the New Zealand 
species even this is absent. Further details concerning the frond-anatomy 
of the New Zealand species cannot here be given, but the above facts have 
been mentioned to indicate that the multi-layered condition of Че lamina 
in the three оа of the коша еЗ consideration may, а , bea 
ialized and not a primitive fea This point will again be а to. 
No doubt the multi-layered alien of the lamina in these three species 
assists them, even in the absence of the ability to modify the frond-form, 
to endure the mid-epiphytic station, by ensuring a supply of water within 
the frond. 
