Herriott. — Plants from the Southern Islands. 383 



common in the grasses and sedges, also in Astelia and Luzula, 

 and in the spiral leaves of the young shoots of Epilobium. Under 

 this head also may be classed the peculiar cushion-like plants 

 of Colobanthus and PhyllacJine. 



(3.) The anatomical modifications of the epidermis of the 

 leaf itself, (a.) A well-developed cuticle. This may be smooth 

 or strongly wrinkled. A wrinkled cuticle serves the purpose of 

 reflecting the light -rays, so that they do not strike down directly 

 on to the chlorophyll tissue below. Such a cuticle is found in 

 Ligusticum and Coprosma, amongst others. In Accena and Poa 

 foliosa the same purpose is answered by the peculiar outgrowth 

 of the epidermal cells into short papillae, which are provided 

 with greatly thickened outer walls, (b.) The great develop- 

 ment of hairs as outgrowths of the epidermal cells (Myosotis, 

 Olearia, Ranunculus, &c), or of th.e deeper tissues, as in Stil- 

 bocarpa. (c.) The position of the stomata. 



(4.) Succulence of the leaf. " A succulent plant loses water 

 much less readily, since the water-tissue gives up its supply 

 reluctantly. In some cases succulence is due to the presence of 

 mucilaginous slime in the cells of the water-tissue, which greedily 

 absorbs and tenaciously retains water."* Here may be classed 

 the bog xerophytes, Colobanthus subulatus and PhyllacJine clavi- 

 gera, and also Epilobium, Ranunculus pinguis, Myosotis, and 

 Astelia. 



(5.) Structure of the chlorenchyma. In the majority of the 

 plants examined the palisade tissue was strongly developed, con- 

 sisting of from two to three layers. In Ligusticum antipodum, 

 PhyllacJine, Astelia, and Scirpus it is not developed, but its 

 place is occupied by a more or less compact tissue composed of 

 rounded cells, which probably acts in something the same way. 



(6.) Presence of oil. Oil-globules are found in the mesophyll 

 tissue, and sometimes in the epidermal cells of the two species 

 of Coprosma, Olearia, Veronica benthami, and Astelia. It has 

 been suggested that the secretion of ethereal oils aids the plant 

 in resisting the ill effects of a heated atmosphere, since " minute 

 quantities of such oils diffused through the air are capable of 

 arresting radiant heat."f 



(7.) Another modification of interest in the leaf-structure is 

 the development of stereom tissue. This is seen best in the 

 species of Ligusticum. It gives rigidity to the leaves, and pro- 

 bably is a protection against the mechanical effects of the wind. 

 In some other species it is developed in connection with the 

 vascular bundles, as in Acaina, Epilobium, Olearia, Luzula, and 



* Kearney (1901). p. 367. 

 t See Henslow (1895), p. 82. 



