Low. — On Haastia pulvinaris. 155 



arranged at right angles to the surface, but they are not of the 

 usual palisade form, being more rounded. Instead of the 

 spongy parenchyma there are only one or two layers of cells 

 bordering on the epidermis, and the rest of the space is 

 occupied only by air. 



The vascular bundles have the same conformation in the 

 tip as in the base, and each is still accompanied by a resin- 

 passage. Towards the tip the bundles are small, the spiral 

 elements being most noticeable. There is a close network of 

 them, one entering each projection, and one lying between 

 each two adjacent projections. 



The hairs on the leaves are of interest ; they occur only 

 where needed for protection — that is, on the lower and outer 

 surface of the base and on both surfaces of the tip. They are 

 multicellular, and each springs from a single epidermal cell. 

 The young hair is composed of only a few cells, each with 

 abundant protoplasm and nucleus. The terminal cell is 

 larger than the rest, and forms an enlarged, rounded tip. It 

 is densely filled with protoplasm, and cuts off new cells from 

 Its base (fig. XIII., h), so that in time it comes to consist of 

 from ten to twelve cells, or even more. All the cells, except 

 three or four at the base, increase greatly in length ; their 

 walls are cuticularised, and the tip becomes pointed. The 

 basal cells sometimes retain a nucleus and remains of proto- 

 plasmic matter, but the rest of the cells entirely lose all trace 

 of nucleus and protoplasmic matter. The basal cells are 

 intimately connected, but the longer cells are only loosely 

 jointed together ; their tips, which are pointed and covered 

 with pits, in many cases slide past each other, cohering very 

 loosely (fig. XIII., B). In some cases peculiar double hairs 

 are formed (fig. XIII., C). 



4. Habitat and Eelation to Environment. 



Haastia pidvinaris is an alpine plant, inhabiting the 

 mountains of South Nelson, at an altitude of from 5,000 ft. to 

 6,000ft. The conditions under which it grows are these: It 

 lives on those shingle-slips that are such a characteristic 

 feature of the eastern side of the New Zealand Alps. They 

 are composed of loose, dry shingle, and their conformation is 

 being continually altered by the slippery nature of the shingle. 

 The upper layers of the shingle are dry, and in summer are 

 burning hot, but the lower layers are wet, and supplied with a 

 never-failing supply of water. 



Situated as it is, the foes' from which Haastia has most to 

 fear are the physical conditions of its environment, the ex- 

 tremes of temperature, the violent wind-storms at all seasons 

 of the year, and the total want of any kind of shelter. The 

 plant has adapted itself so as to be able to resist these in- 



