Cockayne. — Plants of Chatham Island. 283 



esculenta to one in which that fern and Gleichenia circinata 

 occur in almost equal quantities. 



Lakes. 



It may be remembered that I included the lowland lakes 

 with the lagoons ; the lakes here to be considered are those of 

 the tableland. It seems very probable that such sheets of 

 water were more numerous earlier in the history of Chat- 

 ham Island, and that now they are transformed into bogs; but 

 I can bring forward no direct evidence on this point. At the 

 present time, in one instance — that of Lake Te Kua Taupo — 

 the water is on one side actually gaining on the land through 

 the beating of its waves against the soft peaty ground, 

 which falls in large masses into the lake, bearing with it its 

 vegetation. Where this steep bank oi the lake possesses an 

 unbroken surface grow in considerable quantities a species 

 of Veronica of a spreading habit and Aciphylla traversii, both 

 of which plants are in such a position safe from the attacks of 

 sheep. The water of these lakes is, like all the other water of 

 the island, dark-brown in colour. I noted no aquatic plants 

 of any kind. In the shallow water near the margin of Lake 

 Rangatapu, the largest of the tableland lakes, grow Carex 

 sp. and stunted Phormium ten ax. Here lake and bog join — 

 the one gradually merging into the other. 



Aciphylla traversii was evidently originally a bog plant, as 

 evidenced by its reproduction in certain bogs after tire, but to 

 which formation it belonged I cannot say. Its leaves are 

 certainly altogether more flaccid than the New Zealand A. 

 colensoi, but they are more rigid than I had been led to 

 expect. The apex of the leaves is pointed, but it is quite soft, 

 and will not prick the skin even when forcibly pressed against 

 it. The plants vary considerably in size, and the female 

 plant is taller than the male. The largest plants seen mea- 

 sured 80 cm. tall for the female and 33 cm. for the male. 

 The leaves of the female were 34 cm. long, with pinnae 17 cm. 

 long. A transverse section of the leaf shows an extreme 

 xerophytic structure. The guard-cells of the stomata are 

 sunken, the cuticle is extremely thick ; wedge-shaped masses 

 of stereome abut on the resin passages, and these on the 

 vascular bundles, alternating with and separating the palisade 

 parenchyma, while the interior of the leaf consists of rather 

 loose spongy parenchyma, which is completely surrounded by 

 the stereome and palisade parenchyma. This xerophvtic 

 structure of Aciphylla in the Chathams was considered by 

 Diels as quite out of keeping with the present climatic condi- 

 tions (16, p. 288), and that is quite true; but, as 1 show, the 

 edaphic conditions are eminently xerophytic, and can well 

 account for its structure. 



