ARID PORTIONS OF SOUTH AUSTRALIA. 



113 



A "composite" leaf constructed upon the average length and width 

 of the leaves of 30 representative species growing in the desert-semi- 

 arid regions of South Australia has a length of 64 mm. and a breadth 

 of 5 mm., giving the length-breadth ratio nearly 13 to 1. Measure- 

 ments on the phyllodia of 16 species of Acacia give an average length 

 of 84 mm. and an average width of 3.5 mm., or a ratio of length to 

 width of 24 to 1. The average leaf-area was not determined in either 

 class. In another series of 29 species both leaves and phyllodia were 

 measured and the area computed. In this case the ratio of area to 

 length was 4.7 to 1. For the leaf sizes observed, it would appear, 

 therefore, that the ratio of area to length is greatly under that to be 

 expected in species growing under moist conditions — that is, in species 

 which bear leaves with equal transpiring surface, or, in other words, 

 with better developed lamina. The length-width and the area-length 

 ratios, for this reason, may possibly constitute an iudex of the degree 

 of xerophylly of the species. Measurements of leaf and phyllodium 

 sizes are given in table 16. 



Table 16. — Leaf measurements, desert-arid perennials of South Australia. 



Species. 



Length. 



Width. 



Area. 



Species. 



Length. 



Width. 



Area. 



Aoacia aneura 



aneura (narrow form) 



brachystachya 



calamifolia 



cambadgei 



colletioides 



iteaphylla 



kampeana 



linophylla 



oBwaldii 



pycnantha 



randelliana 



rigens 



saliciana 



sentis 



stenophylla 



tarculiensis 



tetragonophylla 



Dodontea attenuata 



Eremophila alternifolia 



brownii 



freelingii 



latrobei 



longifolia 



neglecta 



oppositifolia 



paisleyl 



mm. 

 57 

 55 



100 

 67 

 20 

 12 

 88 

 64 



140 

 47 



110 

 70 

 85 

 75 

 31 



375 

 34 

 30 

 85 

 34 

 26 

 55 

 32 

 80 

 46 

 44 

 28 



mm. 



8 



2.5 



1.6 



1 



8 



1 



6 



7 



1.5 



4 

 26.6 



2 



1.5 



5 



3.5 



5 

 10 



1 



3 



2 



4 



7 



1.5 



5 



5 



1.7 



2 



iq. mm. 

 350 

 100 

 140 



65 

 140 



12 

 350 

 410 

 210 

 175 

 1,050 

 130 

 120 

 350 

 100 

 1,700 

 300 



30 

 200 



30 

 110 

 230 



32 

 230 

 190 



66 



60 



Eucalyptus inciassata var. 



dumo&a 



leucoxylon var. 

 macTocarpa . . 



odorata 



oleosa 



Fusanus aeuminatus 



spicatua 



Geigera parviflora 



Gravillea stenobotrya 



Hakea leucoptera 



multilineata 



HeterodendTum olesf olium . 



Jasminum lineara 



Leptospermuia Isvigatum 

 var minus 



Melaleuca glomerata 



uncinata 



parviflora 



Myopomm platycaipum . . . 



Olearia muelleri 



Pholidia scoparia 



87 



90 



75 



86 



72 



47 



47 



135 



72 



210 



110 



26 

 20 

 25 

 9 

 67 

 90 

 20 



18 



26 

 10 

 18 



7 

 10 



3.6 



1.5 



2 



6 

 14 



6 



5 

 1 

 1 

 1 

 7 

 6 

 1 



tg. mm. 

 1,280 



1,400 

 650 



1,000 

 300 

 290 

 160 

 190 

 140 



1,200 



1,080 

 450 



95 

 18 

 22 

 7 

 450 

 26 

 18 



