Pegg. — Ecological Study of New Zealand Sand-dune. Plants. 163 



(c.) Anatomy. 



Stem a solid cylinder, consisting of epidermis, chlorenckyma and 

 stereome, fibro -vascular bundles, and pith. 



Epidermis : Cuticle very thick ; stomata numerous, above the bands of 

 chlorenchyma, sunken, subsidiary cells present. 



Chlorenchyma : A ring of bands alternating with stereome ; about two 

 to three layers of palisade cells, bands about six cells wide. 



Stereome well developed ; thin bands between chlorenchyma bands, join- 

 ing into a thick cylinder internal to the chlorenchyma. 



Fibro-vascular bundles occur in three rings. The outer ring consists of 

 very small bundles in the inner ends of the narrow stereome bands between 

 the groups of chlorenchyma. The second ring is embedded in the stereome 

 cylinder, and the third ring of larger vascular bundles in the pith, with 

 patches of stereome adjoining the bundles and connected with the stereome 

 cylinder. In transverse sections stained with haematoxylin and saffranin, 

 the phloem and smaller xylem elements are apparent, but the larger xylem 

 vessels appear the same as the surrounding pith. 



Pericycle apparent, consisting of a discontinuous ring of cells between 

 the chlorenchyma and the stereome cylinder, and interrupted at the 

 stereome bands. Internal to the stereome is a cylinder of thick-walled 

 polygonal cells, separated by a ring of cells resembling stereome from an 

 inner mass of large thin-walled polygonal cells in the centre of the stem. 



(d.) Conclusion. 



Leptocarpus simplex shows the following xerophytic characters : Tussock 

 form (this has already been discussed in connection with Scirpus nodosus). 

 reduction of leaves, and stems taking on the function of photosynthesis ; 

 very thick cuticle, sunken stomata ; compact palisade cells, stereome strongly 

 developed. 



The plant, therefore, seems fitted for any xerophytic position, and yet, 

 on the dunes, it grows in moist hollows. Its xerophytic characters are 

 therefore much more in harmony with its halophytic habitat than with its 

 position in the sand-hollow. 



9. Pimelea arenaria. 



(a.) Habitat. 



Only two shrubs of Pimelea arenaria were found, though it is common 

 in New Zealand dune areas generally ; these were at the extreme south end 

 of the beach, near the Sumner Estuary. They grew on the active dune, in 

 exposed position, among Scirpus frondosus. 



(b.) Growth-form. 



A leafy, much-branched, spreading, and rather procumbent shrub. The 

 lower part of the stem is low-growing, the upper part erect and thickly 

 leaved, with corymbose branching. Leaves at top of branches closely 

 pressed together, overlapping one another, with under-surface outwards, 

 covered with shiny white hairs. 



Stems woody, flexible, dark brown, lower part leafless, upper twigs leafy 

 for about 4 in. from top, tufts of hairs in axils of branches, and upper twigs 

 hairy. 



6* 



