48 XEROPHYTIC NATIVE GRASSES, 



bundles are open above and below, and bounded by hypoderma. 

 The special forms of secondary bundles contain phloem only, and 

 are bounded, both on the dorsal and ventral surfaces, by hypo- 

 derma. These are the most numerous in the leaf. The secondary 

 bundles are completely enclosed, contain phloem only, and have 

 no hypoderma either on the dorsal or vential surfaces. As will 

 be seen from Fig. 4, the arrangement of the bundles is irregular; 

 two primary bundles may occur consecutively, the only difference 

 being in the larger size of one of them. 



Between each pair of bundles, colourless parenchyma-cells 

 extend for almost the whole distance between the two surfaces. 

 These cells are large, irregular in size, and separated in all cases 

 from the chlorophyll-bearing parenchyma by palisade-tissue. 



Conclusion. — A comparison of the structure of the leaf of this 

 grass with that of Spinifex hirsutus presents some interesting 

 features. The development of hypoderma in Astrehla pectinata 

 is much greater than in S. hirsutus. This hypoderma (stereome), 

 besides aiding in the mechanical strengthening of the leaf, also 

 helps to repress transpiration The characteristic bands of 

 colourless parenchyma-cells, present in this grass, are absent in 

 *S'. hirsutus. It is probable that these bands of cells are utilised 

 for the assimilation of the palisade-tissue. In the field, a note- 

 worthy feature of the grass is the rapid development of new 

 leaves from every node of the stem. The arrangement and dis- 

 tribution of the colourless parenchyma would allow light to 

 penetrate readily into the palisade-tissue, even in the roUed-up 

 position of the leaf-bud, and thus materially aid in the develop- 

 ment of the leaf. 



Another feature distinguishing it from >S'. hirsutus is the 

 undepressed nature of the stomata. 



The means adapted for rigidity, assimilation, and xerophytism 

 in A. pecti7iata are thus different from those of the halophytic 

 Spinifex, previously under review. 



Neurachnk Mitchelliana Nees. 

 Hab. — Interior of all the States, except Tasmania and Western 

 Australia. In this State, it seems to be more common on the 

 red than on the black soils. 



