Betts. — Autecology of Plants of Peridofite Belt, Nelson. 303 



I. 



Stomata are confined to the upper surface, where they are found only 

 in the furrows. They are sunken below the level of the epidermal cells, 

 and the guard-cells are small and have very thick cell-walls. The epi- 

 dermal cells in the furrow are somewhat pear-shaped, and their walls are 

 irregularly thickened, the result being a number of short papillae which 

 serve to protect the stomata. 



At the base of each furrow there are 3-5 large cells, which form a 

 pidvinus. The cells of the pulvinus have a very thin cuticle, but the other 

 ejiidermal cells are not cuticularized. 



The chlorenchyma is not differentiated into palisade and spongy tissue. 

 The cells of this tissue are small, more or less polygonal, and very closely 

 packed together. They contain a small number of fairly large chloroplasts. 

 Some of the cells of this tissue contain tannin. 



Below the upper epidermis, in the ridges, there is a hypoderma of very 

 small lignified cells, in which the walls are very thick, so that the lumen 

 is very small. In the middle of the ridge these sclerenchymatous cells 

 are contiijued downwards, forming a band several cells wide, and then 

 forming a sheath above the upper part of the vascular bundle. 



The vascular bundle is surrounded by a sheath of oval lignified cells 

 the inner cell-walls of which are thicker than the outer. The vascular 

 bimdle is of the usual monocotyledonous type, and has all the xylem 

 parenchyma lignified. . 



Below the vascular bundle there is another zone of sclerenchyma, this 

 being continued as a layer from 1 to 5 cells thick above the lower epidermis 

 and below the chlorenchyma. These cells are small and have very small 

 cell-cavities. 



On the upper portion of the leaf there are small, stiff hairs on the lower 

 surface and on the margins of the leaf. These are shown in figs. 31 and 32. 

 They are very stiff, unicellular hairs with very thick stratified cell-waUs, 

 and are formed from the epidermal cells. 



Peduncle. — This is shown diagrammatically in figure 33 (p. 301). The 

 stem is hollow, and all the tissues except the epidermis and the phloem are 

 lignified. This diagram shows the irregular arrangement of the vascular 

 bundles, each of which is surrounded by sclereuchjmaa. 



Fig. 34 gives a more detailed view of part of the stem. 



The epidermis consists of small pear-shaped cells with thickened cell- 

 walls. A fairly thick cuticle is present. 



Beneath the epidermis there is a more or less regular circle of vascular 

 bundles, each of which is surrounded by a large mass of sclerenchyma, 

 . consisting of small cells with very thick cell- walls. 



As we pass inwards the bundles become larger, and the amount of 

 s'clerenchyma around them is not so great. The cells of the sclerenchyma 

 are somewhat larger and have larger cell-cavities. 



The ground-tissue consists of fairly large, more or less regular cells, the 

 walls of which are only slightly thickened and are lignified. These cells are 

 closely arranged, so that there are only very small intercellular air-spaces. 

 The cortical cells near the middle of the stem are somewhat larger, and 

 the cell-walls are thinner. 



Bounding the ground-tissue there is a zone of cells which are very 

 irregular both in shape and in size. These cells are empty and their walls 

 are suberized. 



