Pegg. — Ecological Study of New Zealand Sand-dune Plants. 155 



(d.) Heating of surface sand intense at times, but substratum where 

 moist quite cool at few inches below surface. 



(e.) Frosts are comparatively severe from June to August, — 10° C. 

 having been frequently recorded ; shallow-rooting plants would therefore 

 be subject to lack of water. 



When considering the structure of the dune-plants it must not be 

 forgotten that the hills and hollows, as shown in the above table, offer 

 different conditions, the hills demanding not only a more xerophytic 

 structure than do the hollows, but a tolerance of blown sand on the part of 

 the plants. 



In connection with the amount of salt in the sand of the dunes, it must 

 be noted that T. H. Kearney, in " Are Plants of Sea-beaches and Dunes 

 True Halophytes ? " finds that the sea-beach sand contains a very small 

 quantity indeed of salt ; therefore the sand-dune plants of the seashore are 

 not halophytic. 



D. Plant Descriptions. 



1. Calamagrostis Billardieri. 



(a.) Habitat. 



Found in both active dunes and sand-hollows at the northern portion of 

 the beach. 



(6.) General Form. 



A tufted grass, growing in green patches longer than broad, about 8 in. 

 to over 1 ft high. 



Leaves shorter than the culms, about jin. broad, striate, flat, dorsal 

 surface ridged and furrowed, bright green, sheathing, spreading semi- 

 vertically, tapering to a point. 



Rhizome slender, creeping, with many roots. 



(c.) Leaf-anatomy. 



Epidermis : Dorsal — In transverse section, large round cells on the 

 ridges, five or six very large bulliform cells at the bottom of the furrows ; 

 stomata with subsidiary cells, sunken air-spaces beneath . Ventral — In trans- 

 verse section, large cells, those beneath the mestome bundles projecting, 

 thus forming an irregular surface ; in surface view, long cells alternating 

 with short cells, which sometimes appear as papillae ; cell-walls thick, not 

 undulating. 



Chlorenchyma : Bands, butterfly-shaped in transverse section, alternate 

 with mestome bundles ; cells of irregular shape, rounded or polygonal, with 

 small intercellular spaces. 



Stereome in small subepidermal patches above and beneath the mestome 

 bundles. 



Fibro-vascular bundles of ordinary monocotyledon structure, xylem with 

 two large pitted vessels and smaller elements, and a patch of phloem ; the 

 bundle surrounded by a sheath with thickened inner walls, and a paren- 

 chyma sheath sometimes colourless, sometimes containing chlorophyll- 

 grains. Above and below the bundles there are often small groups of 

 colourless parenchyma cells, adjoining the stereome, and probably function- 

 ing as water-storage cells. The bundles, together with the stereome and 

 water-parenchyma, separate the bands of chlorenchyma. 



