100 Transactions. 



as well as in the presence in the leaf-lamina of close parallel veins with large 

 sheaths of sclerenchyma. In a few species the cuticle is little developed 

 or wanting. This is the case with the two species with undifferentiated 

 mesophyll, Randia stipulosa and Drimys howeana. 



Hypoderm consisting of one to three rows of cells between the upper 

 epidermis and the palisade tissue is developed in a great many of the 

 dominant trees. There is a single row of small cells in Acicalyptus Fullagari 

 and Notelaea quadristaminea, but in the coastal Ochrosia elliptica the cells 

 are very large. A two-layered hypoderm is present in Metrosideros nervulosa, 

 Coprosma putida, Coprosma prisca, and Cryptocarya Gregsoni. In Ficus 

 columnaris the lower two rows of a three-layered epidermis perhaps function 

 as water-tissue. The hypoderm consists of three rows of cells in Lagunaria 

 Patersoni, Negria rhabdothamnoides. and Olearia Mooneyi. 



The mesophyll is not clearly differentiated into palisade and spongy 

 parenchyma in Randia stipulosa and Drimys howeana. There is but a single 

 row of palisade cells in Hemicyclia australasica and Notelaea quadristaminea, 

 but in both cases the cells are large. In all other plants examined the 

 palisade tissue was well developed, being near the upper surface in those 

 species having no hvpoderm, and near the centre of the leaf in those in 

 which a subepidermal aqueous tissue is present. Sclerenchymatous tissue 

 is a feature of the leaves of Dracophyllum Fitzgeraldi, Baloghia lucida. and 

 Metrosideros nervulosa. In all these the leaf-lamina is characterized by 

 the presence of close parallel veins, which consist of vascular bundles 

 ensheathed in sclerenchyma, extending almost across the mesophyll. In 

 Dracophyllum, there is as well a layer of sclerenchyma two cells deep 

 beneath the upper epidermis. 



Classification of Plant Formations. 



Normal conditions of climate and soil on Lord Howe Island favour 

 the growth of temperate rain forest about 20 m. in height. Exposure to 

 constant wind, as on the sea-coast and on the summits of the mountains, 

 causes forest to pass gradually into scrub. But in the former salt spray 

 and in the latter high relative humidity determines the floristic and 

 ecological character of the scrub. Changes in soil give rise to meadow 

 formations. On damp ground a sedge meadow is found, on sandy sea- 

 shore are grasses and herbaceous plants which tolerate salt spray, and in 

 an exposed gap meadow and scrub intermix. Limited time permitted 

 only a cursory examination of the principal plant formations on Lord 

 Howe Island. These will be described under the headings just indicated, 

 while their chief characters and determining factors are expressed in 

 synoptical form below. This scheme, however, makes no provision for 

 the vegetation on cliffs, which constitute such a conspicuous feature in the 

 landscape of Lord Howe Island. But the vegetation there found does 

 not constitute a single formation : it is rather a mixture of formations 

 which have spread from the surrounding area according as exposure, 

 holding-surface, or supply of moisture permits. Thus, when moist soil has 

 collected, shrubs appear ; but where there is not sufficient room for shrubs 

 there will be a collection of herbaceous plants and ferns. Similarly, the 

 course of a stream over the cliffs is marked by the abundance of the large 

 tussocks Gahnia and Cladium, and dry rocky places support Asplenium 

 nidus, and on the rock-faces lichens. 



