118 PLANT HABITS AND HABITATS IN THE 



A. ANETJBA AND A. LINOPHYLLA. 



The phyllodia of these species are long, in the latter species linear, 

 although in one form those of A. aneura are rather broad. Only the 

 narrow form in this species was examined. The structure of the 

 phyllodia in the two species is so much alike that a characterization 

 of that of one only, A. linophylla, will be sufficient. As figure 12 

 indicates, in cross-section the phyllode is oval with crenulate margin. 

 Opposite the elevations of the latter is sclerenchyma which extends 

 to the epidermis, and opposite the hollows are masses of chlorenchyma. 

 The alternation of the two tissues gives rise to the striations charac- 

 teristic of the phyllodia. The sclerenchyma masses reach to the con- 

 ductive tissue, of whatever size or relative importance. There is also 

 mechanical tissue on the inner sides of each of the fibro-vascular bun- 

 dles. Longitudinal sections of the phyllodia show that the latter tissue 

 is only in part fibrous, but that the portion placed near the epidermis 

 is of short cells, cuboid in fact — ^that is, hypoderm. There is a rela- 

 tively large amount of mechanical tissue. The chlorenchyma is com- 

 posed of isolated strands, masses in section, of palisade cells which 

 (as figure 14 indicates) are relatively narrow and long. On the inner 

 side they abut on cuboid cells only, which separate them from the 

 tracheae of the conductive system. On the peripheral side they touch 

 the inner wall of the epidermis where the latter is sharply infolded to 

 form the furrows previously mentioned. The epidermis has relatively 

 thin vertical and ianer walls, and the external wall varies in thickness, 

 being heavy on the ridges and relatively Ught in the furrows. It is 

 in the latter only that stomata are to be found where they are situated 

 on the inner portion of the sides as well as at the bottom. The stomata 

 do not appear to have especial protective devices of and by them- 



EXPLANATIONS OF FIGURES 12 TO 21. 



Fio. 12. Acacia linophylla, transverse section of phyllode, semi-diagrammatic, X72. The large 

 proportion of mechanical tissue is indicated (sc) and the protected position of the 

 chlorenchyma (eft). The relatively heavy covering of hairs is indicated by stippling. 



Fio. 13. Same. Detail of margin of phyllode to show the nature of the sclerenchma and epider- 

 mal cells and the presence of glandular trichomes, X700. 



Fio. 14. Same. Detail of inner portion of chlorenchyma showing its relation' to the fibro- 

 vascular bundle at the left, X700. 



Fio. 15. Acacia confiniia, transverse section of chlorophyll-bearing stem, X52.5. 



Fio. 16. Acacia telragonophylla, cross-section of phyllode, semi-diagrammatic, X85. 



Fio. 17. Castiarina atricta, transverse section, semi-diagrammatic, of chlorophyll-bearing stem, 

 X72. The chlorenchyma is shown partly protected by the heavy epidermis and 

 partly by the furrows with the trichomes, of which the latter are not shown. The 

 enlarged outer ends of the sclerenchyma also act in the same capacity. 



Fio. 18. Eremophila altemifolia, detail of young stem with glandular trichome, X525. 



Fio. 19. Same. TraubVerse section of leaf showing old glandular trichome, heavy epidermis, 

 and its covering of a resinous substance. 



Fio. 20. Eremophila freelingii, semi-diagrammatic transverse section of leaf to show the size and 

 frequency of internal glands (,gl), X52.5. 



Fio. 21. Eremophila rotundifolia, longitudinal section, serai-diagrammatic, XS2.5, to show the 

 relatively large internal glands and the very heavy covering of hairs (<r). 

 In the figures the tissues are designated as foUowa: ch, chlorenchyma; ft, conductive tissue; 



gl, internal gland; hd, hypoderm; ac, sclerenchyma. 



