Climate.

Laing and Oliver, in their introductory notes to a joint paper on the vegetation of the Bealey Basin (1929, pp. 716–718, in summarizing the main features of the climate, have drawn attention to the surprising dryness of the atmosphere and high rate of evaporation in an area of exceptionally high rainfall, which for four consecutive years they give as 160 ins., 201 ins., 205 ins., and 171 ins., respectively. That for 1944 was 170.3 ins. In spite of this high rainfall, the vegetation is highly xerophytic, a fact that characterizes the moss flora also, though probably to a less extent. While discussing the Hymenophyllaceae of the National Park, Holloway (1923, 577–618) gives additional data relative to the climate, and attributes the xerophytic character of the filmy ferns of the Bealey mainly to the drying effect of the south-west winds which so often persist for days at a time.

The vegetation of the Otira Basin is much more mesophytic, due in some measure no doubt to the even greater rainfall (230 ins. in 1944) and higher atmospheric humidity. The rain-bringing winds

are from the north-west, and the fact of their ascending in the Otira and descending in the Bealey, coupled with the further fact that rain frequently falls at Otira when snow is falling at the Pass, probably accounts for the difference both in humidity and in the character of the vegetation.

Winds are frequent and often of gale force. Mist caps the tops of the ridges for some portion of almost every day, the lower level of the mist zone being apparently coincident with the lower level of the Usnea belt, so obvious on clear days from the valley floor.