ARID PORTIONS OF SOUTH AUSTRALIA. 131 



effect is as if the mechanical tissue referred to were embedded in the 

 parenchyma, as in fact it is. At the periphery of this centrally located 

 cell-mass are separated hard-bast fibers which resemble the palisade 

 cells of the chlorenchyma in diameter and usually in length, and which 

 extend through the chlorenchyma to the epidermis (fig. 26). Al- 

 though these fibers occasionally extend well into the centrally placed 

 tissue, they nevertheless are almost wholly confined to the chloren- 

 chyma. The fibers also are usually simple and not branched. In these 

 two particulars they appear to be unlike the sclerenchyma of a similar 

 nature described by Jonsson and referred to by Solereder (1899:801), 

 in which branching occurs, and which is generally scattered through- 

 out the leaf. 



The epidermis is unusually heavy, owing to the greatly thickened 

 cuticle. The stomata are placed on a level with the inner wall of the 

 epidermis and are thus at the bottom of a chimney-like structure 

 composed of the epidermis, mainly of the cuticle (fig. 26). At the 

 inner portion of the stomatal pore, and immediately above the stomata, 

 are thickened papilla? of cell-wall material; these fairly well close 

 the bottom of the stomatal pores (fig. 26). 



In the mature leaves, both of H. multilineata and of H. leucoptera, 

 there do not appear to be trichomes of any kind, but the remains of 

 hairs are occasionally met with, showing that when young the leaves 

 are provided with them. In the last figure referred to, the position 

 of a trichome is indicated by the indentation to the left of the stomatal 

 pore, brought about by the failure of cuticle to form where the hair 

 was situated. An additional note should be made on the stomatal 

 pores. In the material studied there often appear to be pores which 

 are continuous with one another, with the effect that a stomatal chamber 

 containing more than one pore is formed. 



MELALEUCA PARVIFLORA. 



The leaves of Melaleuca parviflora are short and narrow, being about 

 1 mm. in width and 9 mm. in length. A transverse section of the 

 leaves shows the following leading structural features: There is a 

 well-defined chlorenchyma, consisting of narrow and fairly long pali- 

 sade cells, which is similar on both leaf-sides. The leaf interior is 

 composed mostly of chlorophyll-free parenchyma, of good size, which 

 has fairly thick walls and no or few intercellular spaces. Sclerenchyma 

 is to be found associated with the conductive tissue only, and it is not 

 a conspicuous feature. The epidermis has a fairly thick outer wall. 

 The stomata are on both leaf-surfaces and lie at the bottom of pores 

 made of the thickened cuticle of the epidermis. 



PlTTOSPORTJM PHILLYR^EOIDES. 



The leaves of Pittosporum phillyrceoides are linear-oblong, about 8 mm. 

 in width and 120 mm., more or less, in length. The small tree is well 

 covered with them, so that the evaporation surface is not inconsiderable. 



