} a L c Gornell University Library Dthaca, Nem York FROM Canned e Id ifutionw) Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924001347461 PLANT HABITS AND HABITATS IN THE ARID PORTIONS OF SOUTH AUSTRALIA BY WILLIAM AUSTIN CANNON PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON WASHINGTON, 1921 et 5 ¥ 7 s A510 24] CARNEGIE INSTITUTION OF WASHINGTON Pusiication No. 308 PRESS OF GIBSON BROTHERS, INC. WASHINGTON, D. C. CONTENTS. PAGE ist-of Mlustrations ysi.2-sc% gies acinar ego r dt ti dies san nales Gees Seem RES v TtrOMUCHON os.ois. saa a.ciete eats oa gee vn Wee dpa a eed Mina ete Pu IkG ET eTeEE RE 1, PS environment_of the vegetation of Australia................eeeeeeeeeeeees 5 -General physiographical conditions...........00cccccccceccccccecsvevuveceuees 5 Features of the climate of Australia.............0cc ccc eeececseceevucvecueeees 8 EerRR aI al ic ia laces erase testers vdiede a wreie caine obits Gar wash Geom AA as Ee a RE 8 VA DON RUIN so 2c fssdic hiscaere geark wiaoaitrle wusaghBiaveanlAavaua dha lasceTRlaNeue BNO. Ga Gus ees tees nel euidensta ee 14 Relative humidityicccene sows oc naw vvirass sa ne dares Weds sirelee ace voces anes AW BER 15 Light aa Gat GP's aah ea yeiesy i 7a Fersehsas w evaeah ahs Gah uw ewe rial a Siletan ee Sire. we Sitak ) AS SG) Bele cei SS Gpsiest So eave Dewees! ALS aw 16 Sir LOMpereture vs.c 5.00 esisiardelelae the Daas dae ro arin lend ole eo weaeere Hae es Medea 18 Winds: 52554 reso acacia sais ae eases Ras w chee Ge ia a tiavesnussa aan algaid cee Geaeane cree 20 , Subterranean environment........... 00. c cece cece cece ee ener ee eeeeeeetees 20 ‘emperature, moisture, and aeration conditions of the soil,,.............++000 23 be Aeration of thie soil.......... cece eee e eee enone =a eMeeo a Gheeeaune Danae é 24 \___... Temperature OE the SOU sess sok see 5 ssa sinks due seco acdsds dw aaksan'g ala a laren deaneed ae wES 25 —4-Certain characteristics of the vegetation of dry regions........... Mahara lee a ranetin nee 2 31 Physical environment of the. vegetation of South Australia... 00. cece eee eee eee 35 “Physical geography........0..ccceccecuccucuvccucesuecteunteunuceenneenaues 35 Nite Runatala's dis 4 xk sie ae eee waa BAP eee adiew aaa ne vacmieaiaaea eee es 42 CMPCTAtUlO 2! io! snanieg ate ovine gael eae Meueals Glee OG Oe a SE Swe ES nee +42 Rainfall scscesiacpigaetewess aera t.vlecie aaciaveigan vu Vege CAA GAGA RUA at aetna ee 44 effective veirit alos. o3 jac fcoesvaccess wens. Sos desm oseuds arasovens dl doaiete evauhutid Auenorerd Janaldva ane erdiardierae 47 Vegetation and plant habitats in vicinity of Oodnadatta................00cce cece 50 Physlography sec -ceciacacs-hied vs deed dee alae eaves alate eiews Daun heaw eae sue ee eee 50 COMB 18s aic4is oss doa aerate seins Wak g dee BEF eeowle ealacdie tanta a ayelan Ctroleve a guage whew eee SDD Rainfall sciccciccdod.cici vv co paicelnikd Sea bus Meee TN od ogg ha Aw oak oan AO 55 Temperatures sc isis. ace viauavaes cee wats eons ewe sey sas anata s seana anise 56 General features of the flora of South Australia... ........ 0.0... cece eee eee eee ee 57 The northern portion of South Australia..........0 0... cece ete e eee e eee eaeaee 57 Vegetation of the Lake Eyre basin...............cccccecueececcececaceneeeeees 58 Vegetation at Oodnadatta........... ccc cece eee eect neeeeee ieee pena sue eae 58 Vegetation of the plains 2.052 eevee A ae a ee tage ee ee 59 + Vegetation of and about the sandhills............ 2... cece cece cece ene e ee eeees 60 The Copley environment cis s sone eens bed s Cant esi eaa eo eeae ed pews cee eK owe ee 64 Physlooraphy’s sess so.¢sse-ssrese ta sai gis sow 8 acaeareacnaag aos ate wee tae Sis es Poa ae oe oe ore 64 Climate..... ec teike tc ole Ah oh gt SSE Hed S ocd. TON canara ad vel Ata anal Salon Ul ou Tala uard tats at 66 EReirad te 2. yen cine seater tale re toca lees acu a Gener r a ouasae ern aeaolee eae aoe Na 66 oot Wemperatures ence woes eo nee ees es see eae Pee PEE EERE eeORs EEE sees 67 ‘Vegetation of the Copley region.......... 0.0: c cece cece ence nee eneeneeneeenees 67 Vegetation of the “alkali” plains................ 0. cece eee e eee suivganeed vedere 68 ~~~ Root-habits of plants of the plains....................... RD Re 70 Vegetation of the low hills and slopes........... 0: cece eee eee etree eee neeee 73 Mono-specific communities...........--..- cece eee eee eee eeeeee ee 74 Isolated species and mixed communities............ 0... cece cece cere eee 76 Vegetation of the washes............0 cc cece cece een e cece rece neneceneneeee V7 Parasitic phanerogams..¢ i. i.c ose vs sod secede ee eh ie eee saa seen cena se aae es 79 “> Root-habits of plants of the washes........... er aires Mee awh sane emus 80 FD Leaf-form and leaf-sizes......... ccc cece ccc eee tee teen een eeeteeeeneee 80 - / Vegetation of southwestern South'Australia..........0.0 00s cece eee c neon eee eeees 81 ! Vegetation and environment at, Ockig: tea ae ah ecient pare asta Seana 81 Physlographysijccussendanaw ce doves avy one swine Vass eo ee eae ae ty See ee 81 Chiniatey sc caasaieaaaes ntact cee gawars axles tise Ae eee da tua rama eGs Shae e oi 83 ADIGA bG cic c.sasc3 &.o0csesacdusnacoieescutio eaeroissattne namie once Maen de Sieh ae sad ee te 84 getation of the Nullarbor Plain............. 22.02. e eee e ee ee eee eee e tenes 85 Vegetation about Ooldeaic ss ijeésdiaice seis ceisie saree eee tees e cette Seats we ees 86 Transition from the sandhills to the Nullarbor Plain................ccceeeeeces 89 Leaf-form and leaf-size...... 2... c ccc cece cee e eee e ence tees eeeeeeereens 89 - Iv CONTENTS. Vegetation of southwestern South Australia—Continued. PAGE. Vegetation and environment at Tarcoola............. ccc cece seen cence ee cececes 89 Phystographiy seosess es niaie. ce vent oe PRR Ewe LER Cae eee deb aee ee 89 Rainfall and temperature.......... 06... e meee cece sence ee eees iis co GPRS teeta 90 VeSetatiOMs wrsisvsduce-o-2 sesleue Gcvere.s Duvwisveneadeian gia Gaa eucetias dja, /eerean et dae Granada aede So 91 Vegetation and environment at \Port Augustg............... sees cece ener e cece 93 Physioeraph yews: er eas steed kanes 624 MOM eee ta eee ak we REN Tee eee 93 see RAN AML cs, cesses eirantuaicens tenn vee esx cubed dis ast en a labs laoeavcthezettusns © ait aysel gent Se \Suaase xe lease 94 acs Temperature: oo ib vacua tithe tiie 2 ice aiee eases teow me a4 ee cae NSS 94 Vegetation sess ¢ aise’ dace vane os ele Dacia eRe eran eee eee Her se we 94 Sizes and forms of leaves and phyllodia............. 0.0 c eee e cece eee ete ees 96 Vegetation and environment at Quorn... ....... 0. ccc eee e cece eee reece ete nnees 96 Climate: srs s24s ieee ese sk els eR ae eee eee sa eee erase eee 99 Vegetation and habitat......... 0.00. cece eee eee e teen tenet ewes 100 Vegetation of the valleys and of Willochra Plain................ cc eeeeeeeeeee 101 Vegetation ‘of: low hile. << sces ice es wee edie to ies esas soe eee eames Leste 105 Vegetation of the washes............. 0000s eee eeeeneee Fees ttuain Vas hut datiapsscaveeoeakers chee 107 ——™ Root-characters.........ccecccecsceceseceseeeees eS oees Siacteece dneeietdaone panes 107. Mallee and the mallee regions............ cc ccc cece eet e ene e erence teeereeenee 108 Physical and climatic features............- 0.2 c eee e cece ee eee ecto cena eee eees 109 Rainfall and temperature........... 000 c cece eee eee e eet teen tee cece eens 109 Vegetation: iii.¢-< s vo.ck bbws cae bas Bee ts oe oe ees e ERR EES Cee eee Sees ee 110 + Morphological aspects of the xerophytic flora of South Australia................... 111 Leaf-size and leaf-form...........000 ccc cece ene ene ee nese nnn teense ereeeee 111- ~—“«: Features of the roots of South Australian plants........... 0.0.0.0 see ee eee ee ee eee 114 Notes on some structural features of perennials.............-.-. eee cece eee eters 117 The phyllodia in some species of Acacia..........-.. cece cece cent ete teeeeas 117 A. aneura‘and Aj linophylla). o.siccc. ceeds secs ee ees BednleeNaaree eee Nee Hees 118 Acacia continua sinsciess slaw eta act woes koa Gwe ss teks slnes Oeaew ean oetaeee 120 AGA Cla FALCULIENSIS 1.55.0. ecciaso dee tigee a espiaee. 66 Naas ahag aid guel Goa GLa a aea cers Aloud Skewes 122 Acacia tetragonophylla. .esc05. cio. see Rae Ade Se eee ee eed ea ese SAS 123 Notes on certain other species of the region........... 0.0.0 cece cece eee eeeeeeee 124 Bossisawalkeerh 5 o5.< oas POOMPoD weow . Eremophila longifolia on edge of Copley Plain near Leigh’s Creek, Copley. ILLUSTRATIONS. PLATES. . View looking north from O’Halloran’s Mount, Oodnadatta, showing lower plain with upper plain at the extreme right in background. . Lower plain near Oodnadatta, showing ‘gibbers” on the surface and typical de- pression with species of Eremophila. . Eremophila freelingii in a shallow wash on the slope of upper plain near Oodnadatta. . Eremophila freelingii in a shallow wash on the edge of upper plain west of Neales River, Oodnadatta. . Acacia cambadgei in a shallow wash on the slope connecting upper and lower plains west of Neales River, Oodnadatta. . Shoot-tips with leaves, Hremophila freelingti, from upper plain west of Neales River, Oodnadatta. . Shoot-tips with leaves, Zremophila latrobet, from a wash connecting upper and lower plains west of Neales River, Oodnadatta. . Acacia tetragonophylla, near west base of sandhills east of Oodnadatta. . Acacia linophylla on sandhills east of Oodnadatta. . Short channel, Neales River, with Eucalyptus rostrata and Acacia stenophylla, small shrubs, on the banks, Oodnadatta. . Phyllodia of Acacia linophylla from sandhills near Oodnadatta. . Eremophila neglecta near base of sandhills east of Oodnadatta. . Neales River bottoms from the lower plain, Oodnadatta. . Shoot-tips and phyllodia of Acacia tetragonophylla, left, and A. cambadgei, right, from Neales River, Oodnadatta. . Leaves and phyllodia of Acacia stenophylla from Neales River, Oodnadatta. . Prominent development of horizontal roots in Acacia cambadgei, Neales River, Oodnadatta. . Vegetative reproduction in Acacia stenophylla from floodplain, Neales River, Oodna- datta. . Kochia sedifolia on low slope above Copley Plain on Yudnamutana road, Copley. . Zygophyllum fruticosum at edge of Copley Plain by Table Mountain. The trees in the background are Casuarina lepidophloia, Copley. . Nitraria scheberi hillock colonies on Copley Plain. Table Mountain is in the back- ground at left, Copley. . Detail of edge of colony of Nitraria scheberi, showing horizontal prostrate branches by which the hillock colony is extended, Copley. . Shoot-tip of Hremophila freelingit from low hills on Mount Serles road, Copley. . Eremophila oppositifolia, showing leaves and flowers, from rounded low hills on Mount Serles road, Copley. . Pholidia scoparia, “‘broom,’’ from low hills on Mount Serles road east of Copley. . Cassia sturtit, constituting a mono-specific community on Mount Serles road, Copley. . Mono-specific community of Eremophila freelingit, in low hills along Mount Serles road, Copley. . Mono-specific community of Pholidia scoparia in low hills on Mount Serles road, Copley. . Hakea leucoptera on southern slope of Table Mountain, Copley. . Casuarina lepidophloia, or “oak,” at south base of Table Mountain, Copley. Community of Zygophyllum fruticosum near Mount of Light, Copley. Petalostylis labicheoides from south base of Table Mountain, Copley. Casuarina lepidophloia, Copley. Petalostylis labicheoides at south base of Table Mountain, Copley. Shoot habit of Hakea leucoptera, with fruit, from Table Mountain, Copley. ‘ Melaleuca glomerata, the “white” tea-tree, in a small branch of Leigh’s Creek, Mount Serles road, Copley. . Melaleuca parvifiora, the “black’’ tea-tree, near Myrtle Springs road, Copley. Eucalyptus rostrata, the red gum, on Leigh’s Creek, Copley. Eremophila alternifolia at side of small wash near Mount of Light, Copley. v 16, 19, a. , . Eucalyptus oleosa by a wash at the eastern base of Mount Deception Range. The 20, a. "B. Narrow “leaf” form of Acacia aneura, the mulga, at Ooldea. Young fruits are shown 22, A. . Leptospermum levigatum var. minus, in flower, from the Ooldea Soak. . The shrubby Eucalyptus leucoxylon var. macrocarpa in flower, from Station 408 near 23, 24, 9a b> ILLUSTRATIONS. . Shoot-tip showing leaves and fruits of Melaleuca parviflora, or “black’’ tea-tree, from Myrtle Springs road, Copley. . Tip of shoot of Eremophila alternifolia with flowers and leaves, Copley. . Leafy shoot of Acacia varians from a wash east of Copley. . Melaleuca glomerata, “white” tea-tree, from Leigh’s Creek, Copley. Eremophila longifolia, Copley. . Branch of Acacia tetragonophylla with short spinose phyllodia and inflorescence buds, Copley. . Acacia tetragonophylla in low hills on Mount Serles road, east of Copley. 17, a. Leafy shoot-tips with fruit of Fusanus spicatus, the “quandang,” and F. acuminatus, the native “peach,” Mount Deception Range, Copley. . Myoporum platycarpum from low hills in Mount Serles road, Copley. . Shoot-tip with leaves and fruit of Loranthus exocarpi and leafy branch of host, Acacia sentis, Copley. . Loranthus exocarpi, at right, and Eremophila brownit, host, Copley. 18, a. Loranthus quandang, with oval leaves, and the narrow-leaved form of Acacia aneura, the “mulga,”’ its host. From Mount Searles road, east of Copley. . Loranthus linearifolius on Acacia tetragonophylla. The host is shown with character- istic spine-like phyllodia. Copley. . Loranthus exocarpi, with leaves and fruit and shoot-tip of its host, Myoporum platy- carpum, Copley. Acacia aneura, the mulga, at Ooldea. prominent stem base and enlarged crown of the taproot, both characteristics of the “mallee,” are shown. Copley. Detail of branch of Acacia colletioides showing spine-like phyllodia Ooldea. on one of the branches. . Broad “leaf’’ form of Acacia aneura, the mulga, at Ooldea. 21, 4. Eucalyptus pyriformis at Ooldea. Various species of Acacia and the mallee, Fucalyp- tus incrassata var. dumosa, make up the surrounding woody vegetation. The floor is bare. . Eucalyptus leucozylon var. macrocarpa, middle ground, and E. incrassata var. dumosa, _ on the hillside beyond, near Ooldea. Fruits of Eucalyptus pyriformis from Ooldea. The fruits are about 5 cm. in diameter. Ooldea. . Pholidia santalina from mallee community of low ridge west of Quorn. . Callistemon teretifolius, from ridge on Mount Arden road, Quorn. Aphyllous Acacia continua from low hills on the Pichi Richi road, west of Quorn. Tip of branch of Acacia calamifolia, in fruit, showing the linear phyllodia. From open Casuarina forest on the Melrose road, east of Quorn. . Gravillea stenobotrya shoot showing leaves and fruits, from Station 408, near Ooldea. . Leaf habit of Eremophila rotundifolia, Tarcoola. . Tips of a branch of Acacia rigens, with phyllodia, Tarcoola. . A fruiting branch of Acacia tarculiensis showing characteristic phyllodia. From type habitat, Tarcoola. ’ . Acacia rigens, the “myall,” with various halophytes, on plain north of Tarcoola. . Thicket of mallee, Eucalyptus oleosa, on sloping saltbush plain, foothills of the Flinders, east of Port Augusta, near Saltia. . “Beef wood,” Gravillea stenobotrya, on the crest of sandhill by Station 408, near Ooldea. . Forest of Eucalyptus rostrata on Saltia creek, east of Port Augusta. : Pine community, Callitris robusta, at Warren’s Gorge, near Quorn. . View in mallee scrub, about 2 miles north of Quorn. Eucalyptus odorata and K. oleosa in the background. Bunches of Triodia irritans in the foreground. 29, A. . Hakea multilineata on the crest of a sandhill by Station 408, near Ooldea, with Fuca- ILLUSTRATIONS. VII . Branches of Acacia sublanata, showing small and rigid phyllodia, Quorn. . Eutazia empetrifolia, showing the small flowers and linear short leaves, Quorn. . Branches of Acacia pycnantha, the “golden wattle,” showing the character of the large phyllodia, Quorn. . View about 2 miles west of Quorn, taken from a grassy ridge and looking upon a ridge which is covered with mallee. In the intervening valley are a few specimens of Eucalyptus leucoxylon var. pauperita. . Hakea leucoptera on the edge of the mallee scrub, about 2 miles north of Quorn. Small shoots which spring from superficial roots of the larger plants are in the foreground. . Western slope of ridge along Mount Arden road, Quorn, with Triodia irritans and Trichinium, dominant grasses. Dead fruiting stalks of Xanthorrhea semi- plana shown in the foreground; mallee, Eucalyptus sp., in the background. Bossiea walkeri on summit of a sandhill by Station 408, near Ooldea. lyptus incrassata var. dumosa, a mallee, in the flats below. Bunches of spinifex, Triodia irritans, are to be seen between the mallee. . Branch with withered flower-spike and leaves of Hakea multilineata, from Station 408, near Ooldea. . Melaleuca uncinata in fruit, from the sandhills by Station 408, near Ooldea. . A community of Acacia pycnantha, the golden wattle, by a streamway on the Mount Brown road, Quorn. . A large specimen of Eucalyptus leucorylon var. pauperita, by a wash on the Mount Arden road, Quorn. A comparison with the automobile will give an idea of its size. . Vegetative reproduction in Haked leucoptera. A young shoot, removed from the soil, is shown taking its origin from a horizontal root. Quorn. . Exposure of roots of mallee, Hucalyptus sp., by a narrow wash, showing the abun- dance of superficial roots. Along the Mount Arden road, Quorn. . Root exposure of Eucalyptus leucoxylon var. pauperita by erosion of the bank of stream above Warren’s Gorge. The roots were washed out for a distance exceeding 16 meters. Quorn. 32, a. Scattered groups of Melaleuca parviflora, in the mallee scrub near Blanchtown. . Flood plain of the Murray River showing open forest of Hucalyptus rostrata partly submerged, Blanchtown. . View in mallee, Zucalyptus sp., scrub on Murray flats near Blanchtown. FIGURES. Physical divisions of Australia, after Gregory, 1916, to which has been added the 10-inch isohyet. The shaded areas have an altitude of 1,000 feet or more above the sea. Mean annual rainfall map of Australia, adapted from Hunt. . Duration of wet seasons, after Taylor, 1916. ‘The periods shown on the map include those months in which the average rainfall exceeds the geometric mean of the monthly rainfalls.” . Wettest months of the year, after Hunt’s meteorological map of Australia, 1916. . Mean rainfall of Australia for January, after Hunt. . Mean rainfall of Australia for April, after Hunt. . Mean rainfall of Australia for July, after Hunt. . Mean rainfall of Australia for October, after Hunt. Graphs, after Hunt, showing average monthly rainfall and mean monthly evaporation, in inches, for various places in Australia. . Mean humditiy of Australia for January, after Taylor, 1918. . Mean humidity of Australia for July, after Taylor, 1918. . Mean annual evaporation in Australia, after Hunt. . Average yearly temperature of Australia, after Hunt. . Mean temperature of Australia for January, after Hunt. . Mean temperature of Australia for July, after Hunt. Vill ILLUSTRATIONS. 10. Chief physical divisions and geographical plan of South Australia, after Howchin and Gregory, with the 5-, 10-, and 15-inch isohyets. 11. Graphs showing the annual (total) and “non-effective” rainfall for 1901-1906 at Oodnadatta (a), Copley (6), and Quorn (c), South Australia, based on records supplied by the Adelaide office of the Commonwealth Bureau of Meteorology. 12, Acacia linophylla, transverse section of phyllode, semi-diagrammatic, X 72. The large proportion of mechanical tissue is indicated (sc), and the protected position of the chlorenchyma (ch). The relatively heavy covering of hairs is indicated by the stippling. 13. Same. Detail of margin of phyllode to show the nature of the sclerenchyma and epidermal cells and the presence of glandular trichomes, 700. 14, Same. Detail of inner portion of chlorenchyma showing its relation to the fibro- vascular bundle at the left, x 700. 15. Acacia continua, transverse section of chlorophyll-bearing stem, X 52.5. 16. Acacia tetragonophylla, cross-section of phyllode, semi-diagrammatic, X 85. 17. Casuarina stricta, transverse section, semi-diagrammatic, of chlorophyll-bearing stem, X 72. 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. 18. Eremophila alternifolia, detail of young stem with glandular trichome, X 52.5. 19. Same. Transverse section of leaf showing old glandular trichome, heavy epidermis, and its covering of a resinous substance. 20. Eremophila freelingii, semi-diagrammatic transverse section of leaf to show the size and frequency of internal glands (gl), X 52.5. 21. Eremophila rotundifolia, longitudinal section, semi-diagrammatic, X 52.5, to show the relatively large internal glands and the very heavy covering of hairs (ér). 22. Fusanus acuminatus, fragment of leaf showing chlorenchyma and a group of tracheids, X 350. 23. Same. Cross-section of leaf to show the heavy epidermis consisting of two layers of cells, X 350. 24. Gravillea stenobotrya, semi-diagrammatic transverse section of leaf. The various tissues are as indicated. Trichomes and stomata are confined to the ventral side, X 52.5. 25. Same. Detail of leaf, dorsal side, in cross-section, to show the greatly elongated epidermal cells and well-marked palisades, X 350. 26. Hakea leucoptera, ieaf fragment, in transverse section, with very heavy epidermis and deeply sunken stoma and papillate processes in stomatal canal. The presence of sclerenchymatous fibers in the palisade chlorenchyma is shown. X 350. 27. Hakea multilineata, semi-diagrammatic cross-section of leaf. The prominent devel- opment of mechanical tissue and dorsiventral nature of the leaf structure are indicated. X 52.5. 28. Same. Fragment of leaf, cross-section, to show heavy epidermis, deeply sunken stoma, and pronounced palisade character of the chlorenchyma, X 350. 29. Pittosporum phyllyreoides, fragment of dorsal side of leaf, transverse section, to show the 2- or 3-layered epidermis, X 350. 30. Same, ventral side of leaf. The heavy outer epidermal wall, the single cell layer of the epidermis, and the superficially placed stoma are indicated. > 350. 31. Triodia irritans, transverse section of leaf, semi-diagrammatic, showing its infolded condition and the position and relative abundance of the main tissues, X 85. In figures 12 to 31 the tissues are designated as follows: ch, chlorenchyma; fz, conductive tissue; gl, internal gland; hd, hypoderm; sc, sclerenchyma; ep, epidermis; fo, fibro-vascular tissue. Al ” PLANT HABITS AND HABITATS IN THE ARID PORTIONS OF SOUTH AUSTRALIA. INTRODUCTION. Australia, especially South Australia, holds much of interest to the student of the vegetation of arid regions. {Where rain is abundant plants compete with one another in a very real way for room in which to live and for sunlight by which they gain energy for various life processes, but _in regions_of scanty rainfall, as in. portions. of South Australia, there is abundance of room and of Tight. Here the ‘ “struggle” is associated with the water relation; it is that of the i individual plant with an arid environment, and pot individual with: individual. When viewed from this standpoint the island continent is seen to be the field of a vast botanical experiment in which may be observed the reaction of numerous species and innumerable individuals to a physical en- vironment, a leading characteristic of which is a relatively.small ren supply. [Moreover, owing to the great_age of Australia, it.is possi that nowhere else. have pee) been. pe cia to and influenced by. an unique. The ae region is very extensive. Some idea of its size can be had by the statement that it has nearly as great an area as all Arabia, and as a matter of fact is larger than all other regions of the kind south of the equator. Living and developing under an environment of which the keynote is aridity, the flora of the continent as a whole bears a xerophytic stamp and appears to possess a degree of uniformity which constitutes one of its most marked characteristics. Wherever one goes in Australia, he encounters trees and shrubs with leathery, ever- green leaves. In the better-watered portions the trees are large and numerous and there is an extensive transpiration surface, but in portions less favored in this particular the trees are not large, a shrubby type. of vegetation prevails, and the transpiration surface is also much restricted in area. Between the two extremes there are innumerable intermediate conditions in which the gradations are quantitative rather than qualitative. When studied in some detail, however, there may be founda bewildering variety of adjustments to the environment, often monotonous perhaps in outward appearance, and which have in a measure the force of belying the generalization just made. The physical and biological complexes which enter into our concep- tion of what constitutes an arid, more especially a desert, region are made up of many features. It is true that they center around the important factor of a small water-supply, but they all should be logically included in any definition of such regions with scanty rainfall. 1 oo 2 PLANT HABITS AND HABITATS IN THE Owing, however, in part to the difficulty in evaluating the biological value of the accessory factors, such as light intensity, relative humidity of the air, rate of evaporation, and temperature of the air, and in part to the fact that such secondary factors may change in relative force with changes in the amount of the rainfall, it is difficult to express adequately what constitutes a ‘‘desert,’”’ or even the degree of aridity. Nevertheless it is important to have some method of comparison. Thus, the extremes in amount of rainfall have been used (MacDougal, 1914:175), and the amount of evaporation for any given year has been compared with the precipitation for the same year, and, finally, com- parisons have been instituted between the moisture content of the soil and the rate of evaporation of the air (Shreve, 1915:92). The intensity of the aridity has also been expressed biologically in terms of the relative number of annuals in a region (Paulsen, 1912:159). It was not convenient in the present instance to use these methods, but it appeared necessary nevertheless (mainly for‘convenience in reference) to have some ready means of comparing one region studied with another, and in the end the device was resorted to of using the rainfall only. An arbitrary classification of regions based on the amount of rain was consequently adopted, which is as follows: A region having 5 inches, or less, of rain annually is a desert; one with a rainfall between 5 and 10 inches is arid; and a region in which the amount of rain is be- tween 10 and 15 inches is semi-arid. In all cases, therefore, in which reference is made in the text to regions so designated the appropriate rainfall will at once be understood. The study of plants in the field may be said to proceed mainly along three lines, which, although more or less intermingled, are fundamentally quite different. Thus, the leading emphasis can be placed on the plants as species, and their occurrence (local as well as general) can merely be catalogued; this is plant geography in a narrow sense. Or, the mutual relationships of plants can be investigated ; this is one formal branch of plant ecology. Or, finally, the investigation can take into consideration mainly the relations of plants to the physical environ- ment in which they are placed; this third phase of the general subject is intimately related to experimental researches along lines suggested by field observations and is not to be dissociated from laboratory studies; this can be referred to as physiological plant ecology. It is the last type of ecological research which the writer has had especially in mind when making field studies, and though it has not been practicable to carry out direct experiments on subjects suggested by the observations, it has been of interest and profit to interpret the observations so far as possible in the light of experimental results already accomplished on analogous lines and with analogous plants by various researchers. In addition to viewing the living plants from a physiological stand- point, another point of view has been of use, the comparative. In all instances the plants observed have been studied in the light of the ARID PORTIONS OF SOUTH AUSTRALIA. 3 writer’s previous experiences in the dry portions of North America, in southern Algeria, and in portions of Egypt, and these experiences have been of incalculable assistance in attempts at interpreting the various features of Australian plant life observed. It is impossible adequately to acknowledge the very many kind- nesses shown the writer while in Australia. A friendly and helpful spirit of assistance and cooperation was shown by a large number and on very many occasions; but especial acknowledgment must be given Professor and Mrs. T. G. B. Osborn, of the University of Adelaide, who helped greatly to make the visit pleasant as well as profitable. Dr. and Mrs. R. 8S. Rogers, of Adelaide, well known for their studies on the Orchidacee, acted as guides on several botanical excursions into the Mount Lofty Ranges, and in other ways were helpful. J. M. Black esq., of Adelaide, an authority on South Australian plants, very kindly determined those plants which were collected by the writer. Among them Mr. Black found some new stations and a species of Kochia collected at Copley which was previously undescribed. Men- tion should also be made of the assistance of Alfred Cocks esq., of Adelaide, the former proprietor of “‘Wilgena” station, near which Tarcoola is situated, whose acquaintance with the ‘‘back blocks” of the state is very extensive. Thomas Gill esq., of Adelaide, was of as- sistance in procuring for the writer useful works on Australian explora- tion and in other ways; C. S. Owen-Smith esq., of Adelaide, was also helpful in various ways; and finally, not to mention others, G. A. Hobler esq., and Capt. E. W. Saunders, of the Commonwealth rail- ways, kindly placed conveniences at the writer’s disposal at Ooldea, and were of much assistance in other ways and at other times. Especial acknowledgment must be made of permission to use figures, tables, or data for the presentation of many characteristics of the physical environment of the South Australian plants. Figure 1 is from Australia, 1916, by Professor J. W. Gregory; figure 10 is an adaptation of a figure in the Geography of South Australia, 1909, by Howchin and Gregory. Those noted as being from Hunt are by H. A. Hunt esq., Commonwealth meteorologist, and have been taken from various publications of the Commonwealth Bureau of Meteorology. The figures from Taylor are by Dr. Griffith Taylor, physiographer, Commonwealth Meteorological Office, and arein part from publications of the bureau and in part from other publications as noted. Asa whole the figures were prepared to serve other than botanical ends and in most of them some changes have been made, inconsiderable in certain instances, to suit the needs of the present study. Figure 11 is based on data supplied by the Adelaide office of the Commonwealth Bureau of Meteorology. In the main the climatological data were supplied by the Commonwealth Bureau or were derived from its pub- lications, and in either case acknowledgment is made explicitly in the course of the study. 4 PLANT HABITS AND HABITATS IN THE The following species, determined by J. M. Black esq., were collected at Oodnadatta, Copley, Quorn, Port Augusta, Tarcoola, and Blanch- town, and in the regions contiguous to these places: Acacia aneura F. v. M. brachystachya Benth. calamifolia Sweet. cambadgei R. T. Bake. colletioides A. Cunn. continua Benth. hakeoides A. Cunn. iteaphylla F. v. M. kempeana F. v. M. linophylla W. V. Fitz. oswaldi F. v. M. pycnantha Benth. randelliana W. V. Fitz. rigens A. Cunn. salicina Lindl. sentis F. v. M. stenophylla A. Cunn. sublimata Benth. tarculiensis J. M. Black. varians Benth. Atriplex mumularnum Lindl. quinii F. v. M. spongiosum F. v. M. vesicarium Hew. Bassia, echinopsilla F. v. M. lanicuspis F. v. M. paradoxa F. v. M. Bossiea walkeri F. v. M. Bursaria spinosa Cavan. Calandrinia pusilla Lindl. Callistemon teretifolius F. v. M. Callitris robusta R. Br. Cassia artemioides Gaud. brownii R. Br. eremophila A. Cunn. sturtii R. Br. Cassinia aculeata (Lab.) R. Br. Casuarina lepidophloia F. v. M. stricta Ait. Cheilanthes tenuifolia Schwartz. Dodonza attenuata A. Cunn. bursarifolia Behr et F. v. M. lobulata F. v. M. Enchylena tomentosa R. Br. Eremophila alternifolia R. Br. brownii F. v. M. freelingii F. v. M. latrobei F. v. M. longifolia F. v. M. neglecta J. M. Black. oppositifolia R. Br. paisleyi F. v. M. rotundifolia F. v. M. Eucalyptus incrassata Lebill. var. dumosa Maiden. odorata F. v. M. oleosa F. v. M. rostrata F. v. M. Eutaxia empetrifolia Schlecht. Exocarpus aphylla R. Br. spartea R. Br. Fusanus acuminatus R. Br. spicatus R. Br. Geigera parviflora Lindl. Glycine clandestina Wendl. Gravillea stenobotrya F. v. M. Hakea leucoptera R. Br. multilineata Meiss. Helichrysum spiculatum D. C. Heterodendrum olzefolium Desf. Indigofera australis Wild. var. minor Benth. Jasminum lineare R. Br. Kochia cannoni J. M. Black (n. s.) decaptera F. v. M. eriantha F. v. M. planifolia F. v. M. pyrmidata Benth. sedifolia F. v. M. villosa Lindl. Leptospermum levigatum F. v. M. var. minus. Loranthus exocarpi Behr. linearifolius Hook. pendulus Sieb. quandang Lindl. Melaleuca glomerata F. v. M. parviflora Lindl. Menkea australis Lehm. Myoporum platycarpum R. Br. Nicotiana suaveolens Lehm. Nitraria schceberi L. Olearia muelleri Benth. pimeleoides Benth. pannosa Hook. Pholidia santalina F. v. M. scoparia R. Br. Pimelea microcephala R. Br. Pittosporum phillyreoides D. C. Rhagodia parabolica R. Br. Salicornia tenuis Benth. (n. s. ®). Sceevola collaris F. v. M. Senecio anethifolius A. Cunn. gregorii F. v. M. magnificus F. v. m. Sida corrugata Lindl. Solanum ellipticum R. Br. Templetonia aculeata Benth. egena Sweet. Trichinium incanum R. Br. spathulacum R. Br. Triodia irritans R. Br. Zygophyllum billardieri D. C. crenatum F. v. M. fruticulosum D. C. prismatothecum F. v. M. ARID PORTIONS OF SOUTH AUSTRALIA. 5 PHYSICAL ENVIRONMENT OF THE VEGETATION OF AUSTRALIA. _,_ The vegetational environment of Australia, including the more arid portions, has a complex geographical background. The island | continent is separated biologically, as well as physically, from “other a continents and has been so 0 separated for an immense period of time.. Long geological ages also have passed since a large portion of the suriace was covered by the sea: The physiography is relatively monotonous, as might be expected from the fact that possibly the area may be regarded as a vast peneplain. The latitudinal situation also is of importance in influencing, really in shaping, the leading characteristic of its climate. Projecting as : it does far into the interior, the state of South Australia shares in the general physical « characteristics of the continent, but it also holds ix in certain regards a peculiar relation 1 to the sister States. Its [ts southern, shores a are washed by the cool seas, while the . northern bo boundaries ; are parched and baked under a tropic sun. tt has the most. typically continental climate of all the states (Howchin and Gregory, 1909:17). Such ai are some of the features which have con- stituted and which now constitute the broad characters of the physical environment of the vegetation of Australia, including that of the central state, and under which by physiological reactions there has slowly developed the vegetation familiar to us at the present day. BAI sc GENERAL PHYSIOGRAPHICAL CONDITIONS. The general physiographical conditions of Australia have many points of interest in connection with the present paper. Gregory (1916:25-27) states that: “Australia as a whole is a great plateau land. Itis a fragment of a large continent, the rest of which has been snapped off along great fractures. ane The mountain system is not determined by any dominant lines of folding of the earth’s crust, like those which have formed the Alps and the Himalayas. Australia was folded at an early period in the earth’s history; and all its ancient fold-mountains have long since been worn down. The chief existing features in the relief of Australia are due to vertical earth-movements, by which some parts of the area have been raised to high plateaus and others have sagged downward into deep basins. The margins of the plateaus have been carved into valleys. . . . The eastern margin of the old plateau has been dissected by powerful streams into deep valleys, which are separated by steep-sided and flat-topped ridges; and in some districts river erosion has been so active that very little of the original surface has been left. . Western Australia, on the other hand, owing to its smaller rainfall and feebler rivers, retains more of the old plateau surface. . . . The inner part of the plateau is a vast gently undulating country, with low rounded hills, except where some hard wind-etched boss of rock rises abruptly from the plains. Wide, shallow depressions run together like the converging branches of a river; and these valleys are divided by the irregularities of their floors into basins, which in wet seasons may contain lakes of little depth; but usually they are 6 PLANT HABITS AND HABITATS IN THE sheets of salt-incrusted clay, or damp mud and salt marsh. . . . Owing to the absence of recent fold mountains the relief of the continent depends on the weathering of the old plateau and the formation of highlands and low- lands by the uplift or subsidence of wide tracts of country.” The same writer divides the continent of Australia into the Eastern Highlands, the Great Plains, and the Western Plateau. The rela- tive extent and position of each division is indicated in figure 1. It SIN od to" Work ATE Se" IGREAT ‘ Pages abe Ae PLAINS Fia. 1.—Physical divisions of Australia, after Gregory, 1916, to which has been added the 10-inch isohyet. The shaded areas have an altitude of 1,000 feet or more above the sea. will be seen that the desert-arid regions lie in the western and cen- tral divisions and that possibly half of the area within the 10-inch isohyet has an altitude of 1,000 feet or more. On the other hand, a not inconsiderable proportion of the whole of the desert-arid regions is situated in the artesian basin of the Great Plains regions and is below the level of the sea. The Western Plateau is not level, but several mountain chains rise upon it; certain of these attain to considerable altitude, as, for example, Mount Woodrofe, of the Musgrave Range, which is over 5,000 feet above the sea, approximately 3,000 feet higher than the surrounding plain (Jack, 1915). ARID PORTIONS OF SOUTH AUSTRALIA. 7 To quote Jutson (1914:20), the interior of the great plateau is arid and has no permanent rivers. The drainage runs into shallow basins (with no outlet except at times of great flows of water), called “salt” or “dry” lakes. There is, however, fresh water to be found where the catchment has been suitable, as, for example, the “soaks” like the well- known one at Ooldea, and basins in the rocks, as vividly described by Carnegie (1898:191). But, with the possible exception of the former, these have no significance so far as the vegetation is concerned. As the interior has little rain and no rivers, there is no water table. The picture that the great plateau presents as a whole is therefore a very arid one, both as regards the aerial and the subaerial plant environment. The great plateau is regarded by Jutson (1914:20-21) as being an old, uplifted surface, a vast peneplain, whose surface has been much destroyed, planed down, and often not recognizable. In the southern half of Western Australia the rocks of a very large area are probably pre-Cambrian, while in the southeastern corner they are Mesozoic or early Tertiary (Jutson, I. c.), which is the region known as the Nullarbor Plains. Where the great plateau of the western part of the continent joins the big central artesian basin, the rocks are also of the Mesozoic and more recent ages. As a whole, therefore, the great plateau is of very great geological antiquity. That portion of the desert-arid region which lies within the Great Plains varies in altitude from somewhat below the level of the sea to 1,000 feet or more above it. One of the characteristic physiographical features is the presence of steppes (Spencer and Gillen, 1912:5) or table-lands of Upper Cretaceous and Lower Cretaceous formations (Jack, 1915:13), which connect the Great Plains to the Western Plateau. On the east the plains gradually rise to the highlands of eastern Australia. The sandhills, which are especially to be found to the north and east of Lake Eyre, but occur to the northwest as well, are built of material derived by erosion from the desert sandstone of the steppes, and the “ gibber’’ plains, or stony deserts, also trace their origin to these Cretaceous plateaus and are the residue remaining in place. A most striking feature of the Great Plains regions is the presence of several large lakes which in earlier geological times.contained fresh water but are now saline wastes, usually carrying water only after heavy rains. Of these, Lake Eyre and Lake Eyre South are the largest, covering an area of 5,000 square miles when filled with water (Howchin and Gregory, 1909:100). Lake Eyre receives the discharge of several rivers of intermittent flow. At various places in the Lake Eyre basin natural artesian wells are found whose outlets are raised into small hills through the deposition of minerals held in solution. Also, numerous “‘bores,”’ deep wells, have been sunk for economic purposes. The water that supplies the wells of whatever sort is derived from rains falling in the Eastern Highlands or is chiefly plutonic (Pittman, 1914). 8 PLANT HABITS AND HABITATS IN THE FEATURES OF THE CLIMATE OF AUSTRALIA. RAINFALL. There are four major rainfall regions in Australia, according to Taylor (19187: 10), namely, the summer-rain region of the north, the winter- rain region of the south, a region of uniform rains in the east, and a region of little rain in the center and middle west. The seasonal shifting of the climatic complex north-south, following the declination of the sun, operates to bring about the seasonal rains. Tropical storms, cyclones, reach inland in summer and cover the entire northern portion of the continent. They extend south barely as far as Oodnadatta. The winter storms, on the other hand, affect the southern portion and extend north only about as far as Farina, South Australia (Taylor, 19187: 10). These aecompany the northern extension of the prevailing westerlies which in summer are far to the south of Australia. There is, therefore, a belt of territory running roughly east and west which is beyond the usual reach either of the winter or of the summer rains. This dry central region comprises, according to Taylor, 37 per cent of the area of the continent. TaBLE 1.—Rainfall at the capitals. A Percentage Capital. raineall, No. of of rainfall 7 in inches days rain. | in 6 wettest E months. Adelaide................ 20.88 123 70 Brisbane................ 46.65 130 67.7 HOD art 5c. cs. scsavcesvicovsins eee 23.39 144 55 Melbourne.............. 25.32 133 49 Perth wi sccasouneescascoe ce 0.0% 32.91 115 86.9 By Gney ecsscsresoora.as 056% 24.49 159.5 59.9 The leading characteristics of the rainfall in the humid regions can be illustrated by that at the capitals of the different states. These are summarized in table1. At Adelaide and at Perth rain occurs mostly in the winter season; at Brisbane it is mostly in summer; at Sydney it is mostly in late summer, autumn, and early winter, while at Melbourne and at Hobart it is fairly evenly distributed throughout the year. So far as the well-being of the vegetation as a whole is concerned the reliability of the rains (or the want of this) is of capital importance. And in a general way the reliability of the rains decreases with the decrease in the amount of the rainfall, which it will be seen only serves to intensify the effects of progressive aridity. Thus we find that in the dry interior of the continent there is a mean variation equal to 40 to 50 per cent from the normal (Taylor, 1918}, fig. 4.) In some years very little rain falls at any season, while in others almost the entire yearly rain may fall within a few hours. While the rainfall throughout the interior is as a rule very unreliable, the portion of the dry mid-region ARID PORTIONS OF SOUTH AUSTRALIA. 9 which has the least reliable rainfall, according to the same author, is in Western Australia. At Roeburn, for example, the following extremes in precipitation have been recorded: In the year 1891 the rainfall was 0.13 inch only; in the year 1900, at the opposite extreme, the rainfall amounted to 42 inches. The region of greatest rain variability is roughly equal in extent to that which lies within the 10-inch isohyet, but it is situated somewhat farther north and hence is largely in the region of summer rains. Fig. 2.—Mean annual rainfall map of Australia, adapted from Hunt. It can be seen that with the possible exceptions of the dry interior on the one hand and the humid regions on the other, the precipitation of the continent can be characterized as periodic. There are thus many days in the year when no rain falls and, as just suggested, these may occur in large degree consecutively. The actual number of rainless days may be surprisingly large, as the following will indicate; the figures are for the year 1912 only: In the humid regions the average number of days without rain for 26 stations is 306.2. In the semi-arid regions the average of 24 stations is 332 rainless days, the average for 16 stations in the arid regions is 328.4, and finally, the average number of rainless days in the desert, 6 stations, is 346.4. It is possible that the regular recurrence of rainless periods over most of Australia is a very important factor, although a very complex one, in giving the vegetation as a whole the xerophytic stamp it bears. 10 PLANT HABITS AND HABITATS IN THE TaBLE 2.—Mean monthly and annual rainfall (in inches).* uw] | Jan. | Feb. |Mar. | Apr. | May.| June.|July. | Aug. |Sept. | Oct. |Nov. | Dec. | Year. Oodnadatta: Mean......... 0.71 10.71 |0.57 |0.18 |0.23 |0.64 |0.28 |0.11 10.32 |0.34 10.38 |0.38 | 4.85 Highest....... 5.18 |4.16 [4.32 |1.79 |1.54 |2.77 |1.68 |0.60 |2.21 |2.03 /1.41 |1.79 | 8.92 Lowest........ 0.0 {0.0 |0.0 0.0 |0.0 |0.0 |0.0 {0.0 {0.0 |0.0 j0.0 |0.0 | 1.54 Leigh’s Creek: (Copley) Mean |0.67 |0.52 [0.80 /0.54 |1.06 |1.11 |0.50 |0.69 0.75 |0.47 10.53 |0.76 | 8.40 Highest....... 4.76 |3.05 14.70 |3.78 [5.84 |4.72 12.24 [3.02 |3.58 [2.06 |2.35 |3.78 |15.6 Lowest........ 0.0 10.0 |0.0 {0.0 |0.0 |0.0 {0.0 0.0 0.0 |0.0 |0.0 |0.0 | 1.95 Quorn: Mean......... 0.64 10.45 10.61 [0.96 |1.58 |2.03 j1.57 |1.84 |1.30 |1.32 |0.87 |0.65 |13.8 Highest....... 3.20 |2.53 13.53 |6.38 |6.86 |4.88 (6.15 |5.53 [4.00 |4.44 [5.36 |2.45 |25.7 Lowest........ 0.0 |0.0 |0.0 |0.0 {0.01 |0.23 {0.14 |0.06 0.0 |0.09 (0.0 |0.0 | 7.43 Adelaide: Mean......... 0.72 |0.63 |1.06 {1.85 |2.71 |8.10:12.65 |2.50 |1.98 |1.72 {1.17 [0.96 {21.0 Highest....... 4.00 |2.67 |4.60 |6.78 |7.75 |8.58 |5.38 16.24 |4.64 3.83 [3.55 [3.98 430.8 Lowest........ 0.0 |0.0 |0.0 |0.06 {0.20 {0.42 [0.36 10.35 10.45 /0.17 |0.04 [0.0 /11.3 Kalgoorlie: Mean......... 0.43 |0.73 |0.90 |0.78 |1.31 §1.27'|0.91 |0.90 10.52 |0.79 |0.58 (0.62 | 9.74 Highest.... 2.50 |4.68 |5.02 |3.43 /8.12 |3.00'|2.08 |3.18 |3.29 |3.14 |2.76 |2.57 |16.4 ~ Lowest........ 0.0 0.0 |0.0 |0.0 |0.0 {0.0 {0.22 [0.0 |0.0 |0.0 j0.0 |0.0 | 4.75 I I I ™ Dec.to Mar, N A F vem}, pen’ A F : pr. ie (YEU: ber to Bivahd Feb dein and Feb’ 77 ie SY CMG LY Fia. 3a.—Duration of wet seasons, after Taylor, 1916. ‘The periods shown on the map include those months in which the average rainfall exceeds the geometric mean of monthly rainfalls.” ARID PORTIONS OF SOUTH AUSTRALIA. ls = = danuary February arcl lune Fig. 4a.—Mean rainfall of Australia for January, after Hunt. 11 12 PLANT HABITS AND HABITATS IN THE Wr Yl re) Fig. 4b.—Mean rainfall of Australia for April, after Hunt. a TaBie 3.—Average yearly evaporation and rainfall for representative Australian stations , Evaporation,| Rainfall, oe Evaporation,| Rainfall, Station. inches. inches. Station. inches. inches. Perth. ciiiidecg ets 66.13 33.26 Broken Hill....... 85.63 9.66 Laverton........ 146.57 9.5 Sydney........... 36.91 48.16 Cues esnaiasiian 22 156.02 8.27 Melbourne........ 38.38 25.60 Kalgoorlie....... 87.74 9.40 Brisbane.......... 51.95 47.05 Adelaide......... 54.28 21.66 Hobart........... 32.37 25.50 Alice Springs..... 97.10 10.99 Wiluna........... 149.67 9.94 ARID PORTIONS OF SOUTH AUSTRALIA. P ee 5 fe re i MS, 4 ypc ste } Fig. 5a.—Mean rainfall of Australia for July, after Hunt. TaBLe 4.—Mean monthly and annual evaporation (in inches).* 13 Jan. | Feb. |Mar. | Apr. | May.| June.| July. | Aug. |Sept. | Oct. Dee. | Year. t Alice Springs: Mean......... 12.2 /10.5 | 9.5 | 6.8 | 4.8 | 3.3 | 3.6 | 5.0 | 7.1 | 9.2 10.6 /12.0 | 95.2 Highest mean../15.4 ;13.8 |12.6 | 8.4 | 5.5 | 4.1 | 4.4 | 6.4 | 8.5 |11.7 12.8 |14.1 |108.4 Lowest mean..| 8.1 | 6.5 | 6.9 | 5.0 | 3.7 | 2.6 | 2.3 | 3.9 | 5.9] 5.8 | 8.6 | 8.9 | 84.2 Adelaide: Mean......... 8.9 | 7.3/5.7] 3.38 ][1.9}1.2/1.2); 1.8] 2.8] 4.7] 6.5 | 8.4 | 54.4 Highest mean..{11.2 | 9.1 | 7.2 | 4.9 | 2.8 | 1.8 | 2.3 | 2.7 | 3.8 | 7.3 | 7.8 |10.4 | 60.9 Lowest mean..| 7.3 | 4.9 | 4.2 | 2.1 | 1.2 8 .8 {1.1 ] 2.0] 3.1] 4.8 | 6.5 | 46.6 Eucla: ; Mean......... 6.8 | 6.0] 5.4 | 4.0 | 3.1] 2.5 | 2.6 | 3.4 | 4.41 5.6 | 5.7 | 6.8 | 57.0 Highest mean..| 7.9 | 7.1 | 6.5 | 4.6 | 3.6 | 3.0 | 3.2 | 4.1] 5.5 | 7.1 | 6.7 | 8.3 | 60.9 Lowest mean..| 5.7 | 5.8 | 4.1 | 3.2 | 2.6] 1.9 | 2.3 | 2.7] 3.9 | 4.7 | 5.2 | 6.4 | 52.8 Coolgardie: ‘ Mean......... 12.4 }10.2 | 9.0] 5.8 | 3.7 | 2.4] 2.3 | 3.5 | 5.3 | 7.4 1 9.9 12.5 | 85.0 Highest mean. ./15.1 |14.3 |11.3 | 9.0 | 4.8 | 3.1 | 3.0 | 4.3 | 6.9 | 9.5 {11.6 |17.8 | 96.6 Lowest mean..| 8.9 | 6.4 | 6.2 | 3.5 | 1.7 | 1.6 | 1.1] 2.9 | 3.9 | 4.6] 6.6] 9.1 | 71.9 * Supplied by the Commonwealth Bureau of Meteorology, Central Bureau, Melbourne. 14 PLANT HABITS AND HABITATS IN THE Fig. 56.—Mean rainfall of Australia for October, after Hunt. EVAPORATION. A relatively high rate of evaporation is one of the most striking features of the Australian climate taken as a whole (table 4 and fig. 8a). In a large portion of the continent it exceeds the rainfall, and in certain regions, as indicated by table 3, the difference between evaporation and rainfall may be very great. Moreover, in a fairly large area the annual evaporation is relatively and actually high. Thus in about 40 per cent of the continent the total evaporation is 100 inches or more annually. Since there is a direct relation between the rate of evaporation and the temperature of the air, as well as with other climatic factors, such as relative humidity and rainfall, it follows that there is a regular course run by it during the year. This feature is shown in figure 6. It will be observed that in regions of winter rainfall the course of the monthly evaporation amount is fairly consistently opposed to that of the rain- fall, but that in regions within the zone of summer rains, as at Brisbane, there is more or less coincidence between the course of the two climatic elements. Table 4 is a detailed summary of the mean monthly and annual evaporation amounts, as well as the highest and the lowest means, for 4 stations. ARID PORTIONS OF SOUTH AUSTRALIA. 15 The region having the highest rate of evaporation is in the western part of the central portion of the continent. At Cue, for example, there is a record of 156.02 inches in one year. This amount far exceeds that reported for Aden, on the Indian Ocean, and Calexico, California (MacDougal, 1914:6), but is not so great as reported for Ghardaia, Algeria, which is 5,309.7 mm. or 17.5 feet (Cannon, 1913:9). Ene PERTH ADELAIDE BRISBANE Inches oe : 7 10 8 ‘. ’ . Pi 8 i LS \ / Feed Je= 6 5 . Fa +/[¥lale atta] ot ele [SlalolElRi=[C Zila SSS Seletstol O° SIBSEESISIZIB/SIS/8] [S/EISIEIS/S/S/S/5/8/5/8] 3/2/18 /3/8/3) 2) 8) 8/818 LAVERTON, W. ALICE SPRINCS COOLGARDIE 20 fa 20 18 i 18 i Nn lr 16 7 7 16 ‘ é ‘ i 14 ‘i i L | 14 Hi Aa if ~ & : am 12 - : ; x ' ‘ ry i 40 2 5 ; a 10 i : : F 8 Bs ; a i 8 ‘| . ie \ 6 ; +H ‘ e ; Ie \ Vg N. * 4 4 her Coe \ 7 <7) 2 * — . 0 4 4 = | = = Z(E[S[E(SISISISIRISIEIS| SIE TSIS/Z/S/3/S 15/8/51] |S/EISIS 15/2] 212/515 1318 Fic. 6.—Graphs, after Hunt, showing average monthly rainfall and mean monthly evaporation, in inches, for various places in Australia. Rewative Houmiprry. The relative humidity isopleths when plotted on a map of Australia parallel fairly closely the coast-line (Taylor, 1918?:8). Hence they are concentric. Other interesting features are the relatively large area which lies within the 40 per cent relative humidity isopleth, which is approximately 27 per cent of the continent, and the changes in area of the region included within this isopleth with its north-south seasonal movement. These features are illustrated in figures 7a and 7b. 16 PLANT HABITS AND HABITATS IN THE The average relative humidity (3 p. m. readings) for the year 1912 for arid-subhumid stations, compiled from Hunt (1912), illustrates the wide distribution of the low relative humidities. The average for 13 arid stations gives a relative humidity of 32.3 percent. Theaverage for a like number of semi-arid stations is 37 per cent. And, finally, the average for 9 subhumid stations is 42.1 per cent. Fig. 7a.—Mean humidity of Australia for January, after Taylor, 1918. In summer, when the center of minimum relative humidity is farthest south, practically all of South Australia is included within the 60 per cent relative humidity isopleth, and possibly in over one-half of the state at this season the relative humidity averages 40 per cent or less. Lieut. The amount and quality of light to which plants are exposed, as is well known, are extremely variable. The light in humid regions, for example, is less intense and contains less of the more refrangible rays, the blue, violet, and ultra-violet, than that in arid regions. The light in high latitudes is weaker than that of the tropics. From its geo- graphical position, as well as from the fact that much of the continent is relatively and actually arid, it follows that much of Australia is exposed to an intense light, rich in actinic or chemical rays. In the ARID PORTIONS OF SOUTH AUSTRALIA. 17 Tsay 2! Zr ain Fig. 7b.—Mean humidity of Australia for July, after Taylor, 1918. absence of data dealing directly with the subject we may get some idea of the amount of light as well as of its variation in amount over the continent by comparing the number of hours of sunshine at several representative stations (table 5). TaBLe 5.—Hours of sunshine for representative stations in Australia. Be Mean Greatest Station. f daily amount, |daily amount, oryear 19t2, in hours. in hours in hours. : PEP acceaniveavevnslsteuis qonntes 2,834.3 7.7 13.2 Adelaide’ ¢s-iiscscssicineviuce 2,479.0 6.8 13.9 Alice Springs: iss cccca nda 3,350.0 9.2 12.8 Brisbane: vs4ccuaes seas 2,758.8 7.7 12.7 SY GH 6i iii acc sce cseneacs evdtonce 1,984.5 - 5.4 13.5 Canberra...........-..05. 2,206.9 6.1 12.3 Melbourne............... 1,862.1 5.1 11.3 Hobart: wccsewsmces seems 1,861.6 5.1 11.8 (Hunt, 1912: 625.) { i There is an interesting relation between the light and the reaction of the plant to other environmental factors. In regions having little that the amount of water lost is thereby also reduced. This is carried rainfall especially, the exposed surface of plants is reduced in ee ee) / t ve 18 PLANT HABITS AND HABITATS IN THE to the extreme under desertic conditions. But the plant is under the necessity of manufacturing food through energy, in part derived from light. This calls for a leaf expanse adequate to this end. Therefore . forces are in constant operation which, on the one hand, tend to decrease the extent of leaf surfaces, and on the other tend in the opposite direc- tion. But in the arid regions, as has just been remarked, light’ is abundant and of proper quality, so that a relatively or actually small expanse of leaves, made necessary by the high rate of evaporation, is also sufficient for the manufacture of foods. According to Schimper (1903:714) light in high altitudes, which may have many of the properties of that of the desert, is very intense and is rich in actinic rays. It operates to retard the growth of shoot axes and of foliage. It induces the construction, on the part of the plant, of certain pigments which may possibly act as a screen, and at the same time it may bring about the more rapid destruction of the chlorophyll. The development of palisade cells is apparently forwarded by such conditions as obtain in the mountains and on the desert, thus tending to increase the xerophytic character of the vegetation characteristic of these regions. TEMPERATURE. Australia possesses a very equable climate; indeed, according to Hunt (1914:124), it is the most pacific and equable of all the conti- nents. This in part is owing to its insularity, in part to its geographical position, and in part to the comparatively low relief of its surface. Taylor (1918?:4) makes an interesting comparison as to the temperature on parallel degrees of latitude between Australia and the average for each hemisphere. It appears that the Australian tropics are hotter than the average for either hemisphere. On the other hand, the tem- perate regions of Australia are somewhat hotter than parallel latitudes in other continents of the southern hemisphere, but the opposite is true with regard to Australia and the northern hemisphere. However, one of the hottest regions on the globe, according to the same author, is in Australia. He states that only four localities are known with an aver- age annual temperature over 84° F. Of these, Timbuctu has an average temperature of 84°; from Massowah to Khartum the average is 86°; Tinnevelly, India, has an average temperature of 84.3°, and, finally, the average at Wyndham, northwest Australia, is 84.6° F. In the annual north-south progress of the seasons the 75° isotherm sweeps nearly the entire continent (figs. 9a and 9b). The cooling effects of the sea and of the highlands are to be seen in the curving of the iso- therms. As a whole, however, the interior has relatively high tem- peratures. Table 6 gives some of the highest shade temperatures reported in Australia previous to 1912, and probably among the highest reported anywhere. In table 7 are presented data relative to the temperature at several stations, mainly in regions of small rainfall. ARID PORTIONS OF SOUTH AUSTRALIA. TABLE 6.—Maximum shade temperatures previous to 1912, together with rainfall. srs Rainfall, ° Localities. inehok: Temp.,° F. William Creek...... ‘ 5.46 119.0 Marble Bar......... 13.88 120.5 Walgott............ 18.9 122.2 Strathalbyn......... 10.05 123.2 Bourke............. 14,44 127.0 TaBLE 7.—Temperature, F.* 19 Jan. | Feb. |Mar. | Apr. | May.| June.jJuly. | Aug. |Sept. | Oct. |Nov. | Dec. | Year. William Creek: Meanie iii civausacacne ones 82.9) 82.8) 76.4} 67.3) 59.2) 54.0) 52.3) 56.4) 62.5) 70.3) 77.0] 81.5] 68.6 Highest mean............ 88.9] 89.4! 81.1] 70.0} 62.3] 58.4! 55.6) 61.2) 65.8) 75.0} 83.3) 85.4)..... Lowest mean............. 77.0| 77.3) 71.4] 63.5) 55.0] 49.2) 48.4) 53.4] 56.8) 62.7) 71.8] 76.5!..... Absolute maximum....... 119.0)115.0)110.4/101.5] 93.2) 81.5) 82.5) 95.8/101.0/110. 5/114. 2/116. 4)119.0 Absolute minimum....... 53.0) 52.5] 46.0) 39.0) 29.2) 27.5) 25.8) 25.3) 34.5] 37.0) 41.0] 48.0] 25.3 Mean No. of days over 90 | 24.4] 21.6] 14.4; 3.0] 0.3] 0.0] 0.0} 0.1) 2.1] 8.8] 16.4] 22.9]114.0 Mean No: of nights under | " GO i oid sh San Saacesaeaveves one 0.0; 0.0} 0.0} 0.1] 5.0) 9.9] 15.3) 8.8) 1.3) 0.2) 0.0] 0.0] 40.6 Farina: Means. «cecnaccian.eouues 81.9] 82.0) 75.8) 66.4] 58.4] 52.7] 50.9] 54.8] 60.7) 68.7] 75.5] 80.2) 67.3 Highest mean............ 88.6] 88.2) 79.8) 69.6) 61.3] 57.0] 54.0) 60.6! 63.6) 73.6] 81.7] 83.8]..... Lowest mean............. 77.0| 76.6] 76.0} 62.0] 54.3] 48.7] 47.7] 51.9] 55.6] 61.1) 67.6) 73.9)..... Absolute maximum....... 118.0}114.3]111.1) 98.0} 91.5] 86.0] 78.0] 90.5] 98.2/107.0/111. 5/114. 2/118.0 Absolute minimum....... 53,2] 51.0] 46.5) 39.1) 31.7] 27.3] 28.3) 29.6] 34.0) 37.0} 42.0] 47.5] 27.3 Mean No. of days over 90 | 23.8] 21.7] 14.6) 2.8) 0.1) 0.0} 0.0] 0.0! 1.2; 7.2] 15.2} 21.9/108.5 Mean No. of nights under AO cress tii i etcalehiteed tes.t6 0.0) 0.0} 0.0; 0.2} 5.2) 12.6] 18.5) 12.8) 3.1) 0.2! 0.0) 0.0] 52.6 Point Augusta: Mean 2.5 .tcaclonckiswiocvs ox 77.6| 78.3! 73.4) 66.4] 59.7| 54.6] 52.9} 55.8] 60.5! 66.8] 72.0} 75.9] 66.2 Highest mean............ 83.6] 84.5] 77.2) 71.2) 63.6] 57.9] 55.1) 60.2] 63.2) 71.4, 77.1] 80.1]..... Lowest mean............. 72.8| 73.5) 70.0) 62.4] 56.4] 50.6] 50.4! 53.0] 56.0) 59.3] 65.3] 70.7]..... Absolute maximum....... 114. 8/117.0/110.9) 98.0] 91.2) 80.8] 75.2) 86.4] 94.0/106.3/108.8}114.21117.0 Absolute minimum....... 51.7| 49.1) 48.6] 42.0] 35.0) 32.2) 31.4] 32.0] 38.0) 39.6} 43.0) 48.0) 31.4 Mean No. of days over 90 | 14.4] 13.4) 9.1) 2.9) 0.1; 0.0] 0.0} 0.0, 0.5} 4.7] 9.4) 12.9] 67.4 Mean No. of nights under 40 3 06ea sea caeieks 0.0) 0.0} 0.0) 0.0; 0.8) 3.9) 7.2) 4.11 0.5) 0.1] 0.0) 0.0} 16.6 Adelaide: Means sareots-94 ois a tatteacties os 74.1!) 74.1; 69.9] 63.9] 57.7) 53.4!) 51.6} 54.0! 57.0) 62.0] 67.0] 71.1] 63.0 Highest mean............ 81.3] 83.0} 74.8} 69.3) 61.2] 57.2) 55.7) 58.3) 61.0] 69.6] 72.1) 77.4] 65.2 Lowest mean............. 67.0} 69.1] 65.2) 59.2) 54.2) 49.8! 49.0) 49.9] 52.0) 55.2) 60.8) 65.8] 60.9 Absolute maximum....... 116.3]113.6/108.0] 98.0} 88.3] 76.0] 74.0] 85.0} 90. 7/102. 2/113.5]114. 2/116.3 Absolute minimum....... 45.1| 46.4| 44.8] 39.6] 36.9] 32.5] 32.0] 32.3] 32.7] 36.0] 40.8] 43.0] 32.0 Mean No. of days over 90 | 11.1] 10.1} 6.0) 0.8; 0.0! 0.0) 0.0; 0.0} 0.0; 1.6] 5.1] 8.8] 43.5 Mean No. of days under AO disor ekte octet ies 0.0; 0.0} 0.0) 0.0] 0.6) 2.8) 5.6) 3.4) 1.6) 0.4) 0.0) 0.0] 14.4 Kalgoorlie: Mean: 24 ic ss0eesseeesdex 78.8| 77.6! 73.0] 66.4] 58.8] 53.6] 52.0) 54.8] 59.9! 65.2! 72.3) 77.4] 65.8 Highest mean............ 83.1] 84.3] 77.4] 71.6] 61.6) 56.5) 54.3) 57.7] 63.8) 71.2, 77.8) 81.7] 67.7 Lowest mean............. 72,2) 73.8) 69.8] 60.5) 55.0] 49.4) 49.5) 51.5) 55.8) 61.2} 68.0] 71.0] 64.2 Absolute maximum....... 114, 4/115.0]105.0/101.4! 92.0] 76.8] 80.0) 87.0] 95.0}101.0/110. 2/113. 0/115.0) . Absolute minimum....... 47.1| 48.2] 43.4) 37.0] 34.5) 32.5) 31.4] 32.1) 32.4} 38.2) 38.2) 47.0] 31.4 Mean No. of days over 90 | 19.8] 15.6)110.2) 3.2! 0.0) 0.0] 0.0} 0.0) 0.6) 3.0) 10.6} 18.4] 81.4 Mean No. of nights under A ico siejajerestiteraead. iarateiavene 0.0! 0.0} 0.0} 0.3) 2.8) 6.5/ 11.0} 7.0} 2.7/ 0.6) 0.0} 0.0) 30.9 * Supplied by the Commonwealth Bureau of Meteorology, Central Bureau, Melbourne. 20 PLANT HABITS AND HABITATS IN THE The number of days during which the shade temperature may reach or exceed 90° F. in the central portion of Australia may be very considerable (table 7). For example, in the northern part of Western Australia the maximum shade temperature sometimes exceeds 90° for days or weeks at atime. At William Creek, South Australia, there are, on the average, ° 114 days in each year when the thermometer registers 90° or over. When it is recalled that the relative humidity of the air is a function of the temperature, the significance of such long-continued high tempera- tures for plant growth, more especially in the dry interior, is apparent. The daily range in the temperature of the air is especially striking in regions where the rainfall is relatively small. Thus in 20 stations in Western Australia and South Australia, whose average precipitation is 8.5 inches, the average daily range of temperature is 37° F. WINDS. The action of air currents, both directly and indirectly, upon plants and their environment is of the greatest importance, especially in dry regions. One of the pronounced characteristics of such regions is the prevalence of winds. With little vegetation to impede their way, they are nearly always blowing. During the seasons of rains this is of comparatively little moment to plants, but with the return of dry conditions, particularly during the summer, the winds operate to in- crease the drought in a marked degree; and even in situations more or less remote from the dry interior the ill effects of the ‘‘desert”’ winds can frequently be seen in the withering of vegetation of all kinds. Thus, in southern South Australia, distant from the dry interior over 250 miles, such winds are experienced occasionally and sometimes are disastrous. Evidences of wind action are not wanting in other directions. Crescentic-shaped dunes near Oodnadatta, the surfaces of which bear ripple marks, and the moving of fine earth in other places, as at Copley, where fences are buried beneath it, are further indications that the winds are active as well as forceful. The flattening of the “gibbers,”’ which make up the desert pavement characteristic of large areas in the central portion of the continent, may also be an indirect result of wind action. e pavement itself is the result of the removal by the wind of the finer soil particles, and, in fact, it is generally recognized as probable that the wind is a very important agent of erosion in the dry nterior, as evidenced in a great variety of ways (Jutson, 1914:142). SUBTERRANEAN ENVIRONMENT. The leading habitats of the desertic-semiarid regions are apparently few in number. They are characterized and may be distinguished by their physical nature and chemical content, as well as by their physio- graphical rélations. Thus, there are salt spots, salt plains, and salt slopes in which the soil, often’of rather fine structure, carries an excess of salts. ch saline areas are often, but apparently not always, ARID PORTIONS OF SOUTH AUSTRALIA. 21 associated with poor surface drainage. These areas are so numerous and may be so extensive that they constitute a very important portion of the habitats of the interior. The non-saline habitats are to be dis- tinguished from one another in part by physical and chemical com- position and in part by their physiographical relations. The leading differences between them, at least from a biological point of view, rest mainly on differences in their water-content and (probably also asso- ciated with this) on their relative temperatures. Thus there are stream-ways and flood-plains and often terraces, plains of several levels. The first two are subject to occasional flooding, but the latter may or may not receive water by seepage from still higher ground. Other plains may occupy the highest elevations and thus may have water relations quite different from those of the plains last mentioned. The plains may, or may not, be protected against wind erosion by a covering of coarse stones, “gibbers.’”’ There are also hills and low mountains and the slopes of these. Of the hills, the moving or sta- tionary dunes constitute important features of the physiography of the dry interior. Between the sandy ridges there are often flat “‘clay-pans”’ which have interesting features of their own. Inasmuch as the species to be found in these habitats are often, possibly largely, characteristic of them, the subaerial environment constitutes a very important factor in the environment as a whole. The subaerial environment of plants thus has interesting connection with surface geology and its history would be that of physiography. Without entering into a discussion of this phase of the matter, however, it will be instructive to note certain characteristics of ‘the dynamics of the general subject. Thus, Howchin and Gregory (1909:103) point out: “ An inland basin, like that of Lake Eyre, can not get rid of its worn-down . material, such as occurs when the drainage of the country flows into the sea, whilst from a deficiency of moisture vegetation is scarce and the soil is but loosely held together. From this cause the soil and sand are constantly on the move, and with the ever accumulating products of waste, the highest hills are gradually covered by drift, and the country is ultimately buried under ite own ruins.” ; But the region of the sandhills is not confined to such a depressed area as the great central basin. Thus D. W. Carnegie (1898:178) describes in a very vivid way a sand plain-sandhill region in central Western Australia, nearly 200 miles across in a straight line. Here the general level of the country is considerably above sea-level, but the - drainage is inland, or at any rate not directly to the sea, and it can possibly be described as being undeveloped. Without going into the subject much further, another region can be mentioned having an accumulation of detritus (and sand is here especially in mind), where the drainage is not well defined. This is the Ooldea sandhill region. Here are sand ridges of prominence which alternate with narrow flats over a region about 50 miles wide. Apparently the rains are absorbed 22 PLANT HABITS AND HABITATS IN THE where they fall, as there are no appearances of washing and the main instrument of detrital transportation is the wind, but owing to the fairly abundant vegetation, as will be described below, the moving of the sand, except where the vegetation has been disturbed, is not an important matter. A notable class of plant habitats is that associated with an excessive amount of salts of whatever kind in the soils. The immediate occasion of the accumulation of the salts is also in part inadequate drainage, but coupled with this are high evaporation and small rainfall. Beds of gypsum, hydrous calcium sulphate, and of travertine, or _ desert limestone, calcium carbonate, are frequently to be found in the dry regions. In certain regions outside of Australia, at least, travertine is an important feature of the environment of plants in that it is not easily penetrable by water and constitutes a fairly dry hardpan as a subsoil. By travertine is meant ‘‘a deposit of carbonate of lime, laid down on the surface of the ground by evaporating water containing the substance in solution” (Jutson, 1914:228). In many places the traver- tine is covered by soil and thus constitutes a subsoil. In appearance the travertine strongly resembles the ‘“‘caliche’’ of the more arid portions of the United States, and is probably the same substance. The exact soil horizon where the limestone is formed is in dispute (Livingston, 1906:8). In place of its being deposited on the surface of the soil it may be deposited at the evaporating surface, which, in such an arid country as southern Arizona, at least, probably lies somewhat below that of the soil itself. The nature of the soil is another important factor of the subaerial environment. It is dependent on the nature of the underlying rocks from which the soil was derived by various geologic agencies. As an important feature of the environment of plants it is not confined to regions of small rainfall, but is to be found in the more moist regions as well. Thus Osborn (1914:118) observes in the vegetation of the Mount Lofty Ranges near Adelaide that— “The second range of foothills, rising about 800 feet to a plateau, presents several markedly distinct types of vegetation which appear to be correlated with the geological formation. The slate hills are covered with grassland and scattered ‘gums,’ having a parklike appearance. The absence of under- growth and the maintenance of a sward may be partly due to grazing, but all the difference observable can not be attributed to this cause. Grass is almost. entirely absent from the quartzite hills, which are covered by a scrub of many species of shrubby plants.” Jutson (1914:58), speaking of the vegetation of the central or salt- lake division of Western Australia, which is arid or semi-arid, says: “(It is] divided into two main groups, viz: that growing on the basic and that on the granitic rocks; the former being stronger and of a more varied character and the latter often or mainly of a stunted and monotonous type, except that in its annuals or small shrubs there is often both variety and beauty.” ARID PORTIONS OF SOUTH AUSTRALIA. 23 TEMPERATURE, MOISTURE, AND AERATION CONDITIONS OF THE SOIL. Thecourse of the moisture, aeration, and temperature conditions of the soil are of very great biolgical importance, but, unfortunately, so far as Australia is concerned, only meager data are to be had respecting them. From studies made elsewhere (which are also few) something of their relation to the general problems with which this study in part deals may be drawn; and the interest here lies mainly in the results touching the soils of regions having a small rainfall. As is well known, the three conditions above mentioned are intimately related and it may be remarked that in consequence a modification of one brings changes in the rest. It is also possibly true that, as to the moisture of the soil and its temperature, the maximum of variability finds its apex in dry climates. The moisture conditions of the soil are dependent on a great variety of factors, among which may be mentioned the amount of rainfall, the physical nature of the soil, atmospheric conditions relative to evapora- tion, and the plant cover. The amount of water which a given soil is capable of holding is related to the physical nature of the soil and according to Briggs and Shantz (1912:31) varies from 23.2 to 69.5 per cent of the dry weight of the soil. The smaller amount is that retained in coarse sand and the larger amount is that retained in clay loam, in both instances in op- position to the force of gravity when free water drainage is provided. Not all of the water of such saturated soils, however, is available for the use of plants. Thus the same authors (1911:217) show that, as con- cerned the species experimented with, the amount of water possible of absorption previous to wilting varied with the character of the soil, but was considerably less than the maximum water-content of the soil. Thus, in fine sand the plant used, Kubanka wheat, absorbed 97.01 per cent; in fine sandy loam it absorbed 90.34 per cent; in clay loam it absorbed 83.7 per cent of the water held by these soils when in a good state of tilth. At the time of wilting, therefore, there is in the soil a certain water-residue which varies with the nature of the soil. It would be of interest to know for how long a period, in dry central Australia especially, there is sufficient water in the soils for the use of plants. In Southern Arizona some attention has been paid to this phase of the problem. At Tucson, for example, Livingston (1906:72) has found that at a depth approximating 0.5 meter there is possibly always sufficient moisture for absorption by roots. At least the upper soils, on the other hand, are air-dry in the arid foresummer, when they may contain not over 6.5 per cent of their dry weight of water (Shreve, 1914:21). Thesoil referred to is a fine, brown clay and, from the work of Briggs and Shantz, it would not be expected that the plants-could extract from it more than 85 to 90 per cent of its water-content, leaving a non-available moisture content of 10 to 15 per cent. Therefore, the 24 PLANT HABITS AND HABITATS IN THE amount of moisture in the soil reported on by Shreve could be con- siderably below that available for plants. Accordingly the arid fore- summer in southern Arizona constitutes very largely a resting season for plants. Since this season comprises about 3 months without rain, it can be concluded that as long, or longer, rainless periods as occur in the dry parts of Australia may operate to bring about a condition of ex- treme soil dryness and that under such circumstances only in favorable situations, or in favorable soils, or in species which reach to deeply placed soil moisture, or which have a water-balance, can vegetational activities be carried on. Studies on the relation between the moisture-content of the soil and the condition of permanent wilting of. plants indicate that all species wilt at approximately the same moisture-content in the same soil, other conditions being equal. Thus, contrary to previously accepted belief, plants native to dry regions are unable ‘‘to reduce the water-content of the soil to a lower point than is reached by other plants at the time of wilting” (Briggs and Shantz, 1912: 235). Although possibly the largest percentage of water escapes from the soil through evaporation from its surface, a very considerable amount is lost by reason of transpiration from the plant shoot. This goes on until the limit of water loss is reached only by the establishment of an equilibrium between air and soil, and the final result is the same as if the air and soil were in direct contact (Briggs and Shantz, 1912: 20). Not only does the upper soil layer lose moisture through the plant cover, but the deeper layers as well become dry by the same means. Thus it has been determined (Alway, McDole, and Trumbull, 1919:185) that the moisture of the subsoils may he greatly reduced through the action of deeply rooted plants—that is, whose roots are 5 meters or less in length. Where such deep-rooted perennials are wanting, the sub- soil remains moist. AERATION OF THE SoIL. The aeration of the soil is an environmental factor of plants of much consequence, although it is measured with difficulty and there appears to be no way of expressing it concretely or exactly. Data regarding this phase of environment, therefore, are largely wanting, but it is known in a general way that the soils of the dry regions are, as a whole, well aerated. This follows from the known conditions directly affect- ing air-movements in soils. Among these the following may be men- tioned: Size of the soil grains; compactness of the soil; amount of moisture in the soil; winds and differences in barometric pressure; temperature of the air and of the soil itself; the plant cover. The composition of the soil is also an important feature in its aera- tion. In the upper soil layers the atmosphere of the soil usually has about the same composition (except possibly as to moisture-content) as the atmosphere immediately above it. Under conditions of re- ARID PORTIONS OF SOUTH AUSTRALIA. 25 stricted movement of the air within it, however, it contains less oxygen, but a greater percentage of nitrogen and carbon dioxide. Where such conditions obtain, molecular and not molar gas-movement takes place, gaseous exchange is relatively slow, and soil aeration is least favorable for aerobic organisms. So far as the soils of arid regions are concerned, possibly the most usual cause of poor aeration, in both meanings as above presented, lies in the puddling following rains. Under such conditions the surface is compacted, the soil spaces are filled with water, and mass air-movement ceases. Where this is ac- companied by relatively high soil-temperatures the amount of oxygen in the soil atmosphere rapidly decreases and that of carbon dioxide rapidly increases, following the respirational activities of soil organisms of all kinds. There follow differential reactions by which the course of development may be and in certain species certainly is determined. Under extreme conditions of poor aeration such may become a factor limiting the survival of a species in a given habitat. TEMPERATURE OF THE SOIL. Few data on the temperature of the soil, particularly as to the more arid regions of Australia, are to be had. However, the general fea- tures of the course of the soil-temperature in arid regions are fairly well known. The temperature of the soil varies with a variation in the physical character of the soil, with its moisture-content, and with the depth. Possibly no environmental factor is of greater importance to plant life than this one. Observations on the temperature of the soil, made at the Desert Laboratory (Cannon, 1911: 20), will illustrate the course of the tempera- ture of the soil in a semi-arid climate. The records referred to relate to the temperature taken at two depths, 15 and 30 cm., by means of thermographs. At the lesser depth the daily variation in temperature is about 8° to 12° F. and the maximum annual variation is about 69° F. The period of maximum temperature coincides with that of the highest summer temperature and immediately precedes the rains of that sea- son. With the coming of the rains of summer the soil-temperature immediately falls and it continues to drop gradually until somewhat past midwinter, when the upward movement begins. The rise is gradual until the last of March, when it is somewhat accelerated, and by May the temperature of the soil is nearly that of midsummer. There are, therefore, approximately 3 months each year, the arid foresummer, in which high soil-temperatures occur at a depth of 15 cm. The maximum temperature, depth 15 cm., observed was 105° F. (40.56° C.) and the minimum temperature at that depth was found to be 34° F. (1.11° C.). The temperatures of the soil at a depth of 30 cm. have many features characteristically different from those of. the lesser depth. Thus the daily range in temperature is 2° to 4° F. and the annual variation is about 30° F. The mavimum temperature 26 PLANT HABITS AND HABITATS IN THE recorded for 30 cm. depth was 99° F. (37.22° C.) and the minimum was 44° F. (6.67° C.). The yearly course of the soil-temperatures for this depth is as follows: Beginning with high temperatures of late summer, just before the rains, the temperature drops with the rains and continues the downward movement until March, when a fairly rapid rise begins and persists until the rains of midsummer. Additional records of 60 cm. and 120 cm. depths, unpublished, show noteworthy features, some of which are as follows: In neither case is there a daily variation determinable by the apparatus employed. In both of the greater depths the maximum temperatures are attained (as at the two lesser depths) just before the rains of midsumm:r. At a depth of 60 cm. the maximum temperature observed was 89° F. (31.67° C.) and at a depth of 120 cm. the maximum was 79° F. (26.11° C.). The minimum temperature at a depth of 120 cm. was 56° F. (13.38° C.), and the annual range was observed to be 24° F. The course of the temperature at this depth following the rains of summer is downward until late in winter, when it gradually rises until midsummer. Thus the quick temperature rise in spring characteristic of the soil at a depth of 15 cm. does not occur at the greater depths. The soil of which the temperature at a depth of 15 cm. and 30 cm. was reported on in the preceding paragraph is an adobe clay, and that of which the temperature at greater depths was characterized Fig. 8a.—Mean annual evaporation in Australia, after Hunt. ARID PORTIONS OF SOUTH AUSTRALIA. 27 above was of clay with an admixture of small stones. Soils of other compositions, especially of other physical properties, would give other results. Thus, Hilgard (1906:306), quoting Wollny, states that different soils have summer and winter temperature properties as follows: In summer the sandy soils are warmest, with humous, lime, and loam soils following in the order named. In winter the following order in this regard obtains: humous, lime, loam, and sandy soils. Sandy soils, at least the superficial layers, in summer and in the desert, become intensely hot, according to Hilgard, but at the same time they allow the existence of moisture at a depth of 10 to 12 inches below the surface. Clay soils in the same regions, “being usually in a compacted condi- tion, will show a lower surface temperature and will be warmer and drier at a depth at which sand will still retain abundant moisture and be comparatively cool.” Certain additional features concerning the temperature of the soil should be mentioned. It should be said that the position of the sur- face relatively to the incident heat rays is of some importance. Thus, as is well known, the sun of winter is less effective than that of summer, and slopes may be warmer or colder, depending on their relation to the direction of the rays of heat impinging their surfaces. Only surfaces lying at an angle of 90° to the incident rays receive the maximum heat. When the angle is 30° the amount of heat is about half the maximum, and it rapidly falls with sharper angles (Cannon, 1915*: 213), so that at 15° from the incident rays it is only about 8.5 per cent of the maximum. Fia. 8b.—Average yearly temperature of Australia, after Hunt. 28 PLANT HABITS AND HABITATS IN THE In the preceding summary of temperature differences characteristic of different depths of soil, actual temperatures only were considered ; but another point of view, which is instructive, can be held by a summa- tion or integration of the temperatures, month by month, for different depths. Reference is here made to a depth of 15 cm. and 30 cm. and, in addition, that of 2.6 meters is included for comparison. As a whole, it appears that there is a greater amount of heat at 30 cm. than at 15 cm., although the latter has the higher maximum. And it ap- pears that the rains of summer cause a sharp fall in the total heat, but that in the rainless early autumn the total, if not the monthly maximum, temperatures recover and the final drop in heat comes only with mid-autumn. The relative amount of heat at a depth of 15 cm. and at a depth of 30 cm. is surprisingly close. It is only with con- siderably greater depth that a marked falling off in the total: heat is to be found. Finally, it appears that the total amount of heat is greatest during January at a depth of 2.6 meters. It will be noted that the soil depths above used in the studies on temperature were relatively great. Higher temperatures are known to occur‘at less depths. Thus, Coville and MacDougal (1903: 41) report a temperature of 111° F. (43.89° C.) in volcanic sand and alluvial deposit at a depth of 5 cm. and cite Toumey to the effect that “the temperature of the soil at the depth of one inch near Tucson reaches the temperature of 113° F. (45.0° C.) with a mean average of 104.9° F. Fie. 9a.—Mean temperature of Australia for January, after Hunt. € ARID PORTIONS OF SOUTH AUSTRALIA. 29 (40.5° C.) for the entire month of July.” Even higher temperatures of superficial soils have been reported (Coville and MacDougal, g.v.,p.41). Therefore, at one and the same moment the roots of spe- cies of deeply penetrating root-habit may, near Tucson, be subject to a temperature stress of 33.1° F. (18.3° C.) or over, or more than the total maximum yearly variation at a depth of 30 cm. Owing to the large number of factors which determine the tempera- ture of the soil, it is impossible, in the absence of actual temperature- measurements, to satisfactorily adjudge this important feature of the physical environment of plants. Hann (1903: 43) states that the daily variations in temperature hardly extend one meter into the ground, and that one observation daily at greater depths suffices to give good means. Conversely, all things being equal, it should be possible to roughly evaluate the mean annual temperature of average soils at a depth of one meter from the air means of the latitude. At the middle and higher latitudes, however, Hann states that the soil at a depth of one meter has an annual mean about 1° C. above that of the air. Taking the annual average temperature of the air for Australian regions along 135° east longitude, as given by Taylor (19187: 4), we have, therefore, an estimate of the mean annual temperatures of the soil at a depth of one meter and at different latitudes. These are given in table 8, adapted from Taylor. It will be seen that at the depth given and Fig. 9b.—Mean temperature of Australia for July, after Hunt. fy 30 PLANT HABITS AND HABITATS IN THE between the extreme north and extreme south of the continent of Australia there is a difference of approximately 27° F. in the mean - annual temperature of the soil. It is of interest to note that the mean air-temperatures in the desert are higher at parallel latitudes than those given by Taylor for longi- tude 135°, and probably also the mean temperature of the soil at a depth of 3 feet is higher in the desert. Thus, at William Creek, 28° 55’ south latitude, the yearly mean temperature is. 68.6° F. (20.33° C.), which is 2.6° higher than at latitude 30° along the longitude farther east, as given by Taylor. The summer mean temperature of the air and of the soil at William Creek also is quite as high as at latitude 10°, and the winter mean is quite as low; in fact, it is somewhat lower than the mean in the southern extremity of the continent. Thus, at William Creek the course of the mean air-temperature throughout the year, and probably also of the soil at a depth of one meter, is continental in its range. Table 8 shows the estimated mean annual soil-temperatures, depth one meter, at latitudes given and in regions along 135° east longitude. TABLE 8. Lat. 8. Soil temp. Tropic: oF, 10 82 15 81 20 76 Temperate: 25 70 30 66 35 61 40 55 ARID PORTIONS OF SOUTH AUSTRALIA. 31 CERTAIN CHARACTERISTICS OF THE VEGETATION OF DRY REGIONS. In_externa]_and-internal morphology, as well as in many physio- \ logical processes, the vegetation of regions having a small rainfall is different from that of the humid regions. For instance, the shoot may be greatly reduced both as to size and surface. The constituent members of the shoot may assume fairly vertical positions. The foliage may be largely restricted to the ends of the branches, from which may arise a canopy-form of shoot. The leaves may be wanting or they may be replaced by phyllodia. Succulency may be found in leaf, shoot, and root, or in any of these. Other modifications include the rolli of the leaves of grasses, greatly elongated type of leaves, or phyllodia; and in some forms dissected leaves in which the leaflets or lobes may be considered .the pliysiological equivalent of leaves. In many species the shoots are provided with trichomes of various kinds, which serve as a protection against rapid loss of water from the surface. The trichomes may protect indirectly through the secretion of resinous substances, which coat the surface, especially of young leaves or shoots (Collins, 1918: 255). The roots of xerophytes are as a rule deeply penetrating, but this is not without exceptions. Many forms with water-storage capacity, for example, have roots which lie close to the surface of the ground (Cannon, 1911). Also, perennials may have roots of a dual habit in that some are superficially placed, and some may penetrate deeply The leaves (or their equivalent) of xerophytes are leathery in texture. An examination of their structure shows certain characteristic features, | among which may be mentioned the following: The outer wall of the epidermal cells may be heavy and heavily cutinized and sclerenchyma is well developed. There is usually found palisade tissue and few intercellular spaces. The stomata are protected in various ways, as by being placed at the bottom of tubes, in which case the walls of the tubes may be cutinized. Storage cells for water, which in times of need | yield water slowly to the adjacent cells, are often found. In large, * fleshy species, where the water-storage tissue is well developed, the stored water may be sufficient to enable the plant to live for a period exceeding 73 months in a dry atmosphere and without absorbing additional water (MacDougal, Long, and Brown, 1915: 290). As would be expected from the specialization of the structures of xerophytes, as well as from the leading features of their morphology, the physiological characteristics of the plants of the desert-arid regions have many points of interest. These are largely associated with the water relations of the plants; thus the effects of dryness have been followed in many directions. The growth-rate is less at midday, when the rate of transpiration is high and, relatively speaking, the rate of | water absorption by the plant is low (MacDougal, 1918:59). The © progressive desiccation of the soil and of the tissues in Opuntia versicolor < a 32 PLANT HABITS AND HABITATS IN THE is accompanied by a change in the “relative transpiration,” or tran- spiration power (relation between rate of transpiration and rate of evaporation). Under dry conditions the t/e ratio is greater by day, but under moist conditions it is greater by night (Shreve, E. B., 1915: 79). The fluids of desert plants have a high concentration, as determined by Fitting (1911: 209), Lawrence, Gortner, and Harris (1916:1). The concentration. of the juices varies in relation to local environmental be paruia \ It is least in the arroyos and greatest in the salt spots:\, or example, an average of eight determinations of the density of the juices of plants from the latter habitat gave 37.1 atmospheres. Table: 9 summarizes these results. rad TaBLEe 9.—Osmotic pressure, in atmospheres, of various growth-forms in five habitats of the Tucson region (Harris, 1915: 81). Growth-forma. Arroyos. Canyons. ee Bajadas. | Salt spots. Trees and shrubs........ 17.7 22.4 22.0 34.7 47.9 * | Dwarf shrubs and twiners. 16.6 21.0 21.1 23.9 34.2 Perennial herbs.......... 13.0 14.4 16.8 19.7 Sais Winter annuals.......... 12.9 13.0 15.3 21,1 23.6 Richards (1918: 64) finds that a certain species is more or less suc- culent when growing under dry conditions, whereas the typical forms, under moist conditions, have thin leaves. In every instance the more ent form deyeloped less acid than the form less succulent. starch (MacDougal and Spoehr, 1918': 247). Thus the polysacchar- ides are converted- into anhydrides or wall material under conditions of aridity, or in steculent species, polysaccharides are converted into pentosans or apo These changes, particularly the last, are of great physiological importance to the species, inasmuch as the ‘‘imbi- ' bition” capacity of the polysaccharides is small. Their transformation from this form into that of the pentosans gives the increased capacity (of imbibition) characteristic of the pentosans, so that without any addition of material to a cell, but simply by the loss of water, a change takes place by which the cell is capable of absorbing and holding vastly greater proportions of water. Low water-content of certain cacti results in a condition of general reversion of carbohydrates to polysaccharides The simpler sugars, or monosaccharides, decrease in amount in the plants as the water-content isreduced. With continued low water-content\the pentosans increase decidedly (Spoehr, 1918: 62). \¢="It would appear, therefore, that dryness de itself may profoundly modify the chemical nature of plants exposed to its influence and it may lead, as indicated above, on the one hand to formation of wall material, : ARID PORTIONS OF SOUTH a 33 or on the other to that of material capable of imbibing water in large amounts. Thus a condition of. succulenge . may be induced, and possibly also the formation of mucilage cells frequently found in xerophytes. The presence of heavy cell-walls, and possibly also the condition of spininess characteristic of many plants of dry regions, may thus, at least in part, find‘a.rational explanation. " The temperatures of the airand of the soil are of very great im- portance in many physiological processes of xerophytes as well as other types of plants. Certain of ‘the temperature relations may be here mentioned. For example, the critical temperatures for growth are to a degree specific, and on this fact may depend in part the charac- teristic distribution of the species, its time of vegetative and repro- ductive activity, and, in certain instances, the type of root-system developed (Cannon, 1914: 81, 1914: 83, 1915: 62, 1915:87, 1915°: 211, 1916: 75, 19167: 435, 1917:82). In evaluating the temperature of the soil as an environmental factor the critical temperatures for growth of any given species must be known, as well as the soil-temperatures at the depth normally attained by the roots. The total expected growth during the growing season with the aid of these data can be easily de- termined. In this manner also we may learn the relative efficiency of two stations as regards any species, so far as the soil-temperature is concerned; also, the biological significance of a summation of soil- temperatures may be found by the same means (Cannon, 1917:91). As to the immeiiiate effects of temperature, only a few especially applicable references\need be given. The osmotic pressures increase with an increase.in temperature-and the rate at which-dissolved sub- stances diffuse through protoplasm also depends gh. temperature. The hydrolysis.of starch. is.hastened. by higher. te atures-up to 45° to 50°C. The acid-content is owered with ther. temperatures. The rate of gaseous exchange, in respiration, is’ nearly proportional to the temperature. The maximum hate occurs at about 40° C., and the minimum at 10° to 15° C. (Palladin,A917). The carbohydrate equi- librium of Opuntia sp. depends ix part on the water-content. and carbohydrates, the-monosaccharides (Sposhr, 1917: 73). The rate of water absorption in agar rid in biocolloids increases ith a risé in ‘temperature up ietaeee eels s of the plates,.which occurs near 40° C. in agar and somewhat higher in the biocolloids (Mac- Dougal, 1918: 68). _The position taken in the-ground_by the roots of certain-species has a very definite relation to the aeration conditions-of.the soil (Cannon, 1918:81) and the distribution of cultivated plants (Howard and How- ard, 1915), as well as certain species native to a semi-arid region (Can- non and Free, 1917: 178), may also be directly related to the root re- ea 26 26' 30° t 34 PLANT HABITS AND HABITATS IN THE action to conditions of poor soil-aeration. The_first. noticeable effect of oxygen deprivation to the roots of Coleus sp. is the cessation of the absorption of water (Free and Livingston, 1915:60). This is followed by a cessation of growth and ultimate wilting of the shoot. 130° 132° . 134° 136° 138° 40° = —- ENTRAL PLAINS L. EVRE Of L, BLANCH airs. Sskis PPE Shy Hy SKE ILLOURAW a BABE RN RA SeINE NSS INS ESON GS NA WS SS Formerly, vere”: CRENS SAN Sea AS ANUS T' Kia NS 32" SAW Y Central Plains PWNS X Ld AN au : Western Plateau \ \ = X Wo ; SHINS WW Nullarbor Plains Xe RR WS a [| Gt.Valley of South Australia KS (34°F we Y Pee 3 eK yes Sars teh Highlands of South Australia & CQ ON Ss ead’ S12 BY WW SSeS = Murray Basin as Hoe | | _Y Yedoev aioe * = nq v NS —e Railroads 2) sx vine WSS om =Ancient E.and.W. Mountain Lines woe 36° KANGAROO ISLAND Jeffreys Deep 33° 128° 130° 132° 134° 136° 138° 140° 142° Fic. 10.—Chief physical divisions and geographical plan of South Australia, after Howchin and : Gregory, with the 5, 10, and 15 inch isohyets. 2a* 26° 28° 32° 34° 36° 38° ARID PORTIONS OF SOUTH AUSTRALIA. 35 PHYSICAL ENVIRONMENT OF THE VEGETATION OF SOUTH AUSTRALIA. PHYSICAL GEOGRAPHY. [ The. pera Australia Sa HIN 12.8. per cent of the and longitude 18" a and aoe eee teat there- fore, is wholly included within the temperate zone. In latitude South Australia roughly - corresponds with central. Chili,. Argentina, _and southern Africa, and in the northern hemisphere. with Algeria, southern Spain, and.southern Italy, northern Egypt, Palestine, and the most of Asia Minor,-and northern China and Japan. So far as the climate is concerned, as will be shown below, the state probably most nearly resembles southern California, the Mediterranean region, and southern Africa. | South Australia may be fairly well divided into three physiographic general regions, as indicated, in_ figure I0, page 34. These may be referred to as the western..plateau, the (central and northwestern) highlands, ¢ and the lowlands (of the-south and east). . The western plateau is an eastern, continuation of ‘the great plateau of Western Australia, which embraces about half of the land surface — Of the continent. So far as concerns the portion of the plateau within the borders of South Australia, it can be divided into three leading physiographic formations, which may be referred to as the Bunda... plateau or Nullarbor plains, the Lake Torrens. plateau, and the desert, sandstone - tableland. The country which lies along the Great Australian Bight, and extend- ing about 150 miles inland, constitutes the region known as the Nullar- bor plains, from its supposed treeless character, or Bunda plateau, from the native name for the cliffs. The plateau rises from about 250 feet at the sea to 800 or 1,000 feet along the northernmost portion. It is a limestone plain of Miocene age and constitutes an extension of the older plateau of Western Australia. The Lake Torrens plateau lies to the west of Lake Torrens, or, more exactly, to the west of the great valley of South Australia. It is of limited extent and is made up in part of flat-topped hills west of Point Augusta, known as the Tent Hills. It attains its greatest width just to the west of Lake Torrens (Howchin and Gregory, 1909: 93) and is much older, geologically, than the Nullarbor plains, being of the same age as the Flinders Ranges (Howchin and Gregory, I. c.). The third tableland, the Desert Sandstone, “once extended over most of central and northern Australia. * * * It represents the old land and fresh-water deposits which accumulated after the Cre- taceous sea drained off from central Australia.’”’ The desert sand- stone tableland extends from Copley north and forms the general fea- t 36 PLANT HABITS AND HABITATS IN THE ture of the western side of Lake Eyre. ‘The regular flat-topped hills represent the old land-levels, fragments of which have been preserved from denudation by hard silicious beds that have formed the protecting cappings for the softer beds beneath” (Howchin and Gregory, I. c.). At present this formation is reduced to a triangle, of which the base abuts against the northern end of the highlands of South Australia (Gregory, 1906:64). On the north it extends apparently beyond the confines of South Australia and on the west it reaches to the eastern end of the Everard Ranges. The desert sandstone belongs to the Upper Cretaceous series. According to Jack (1915:41): “The series is made up of sandstone, grit, light, to grey shale, and a little limestone and, as far as it is possible to judge, has a thickness not exceeding 200 feet. * * * Subsequent to the elevation of these beds striking hydro- chemical metamorphosism has taken place under the joint influence of light, rainfall, and warmth, resulting in very extensive silicification of the surface rocks * * * largely responsible for the very characteristic topography of the Upper Cretaceous areas. * * * The presence of this resistant capping of quartzite, chert, or flint has resulted in the formation of table- topped hills and tablelands. The wearing away of the soft underlying shales undermines the indurated beds, which break up to form the stony mantle of the ‘gibber’ plains, and by its presence affords evidence of the former extension of the Upper Cretaceous rocks, even though denudation has proceeded so far as to leave the residual stones resting directly upon the blue shale of the Lower Cretaceous series.” The author goes on to say that the rounded form of the “gibbers”’ is due to the action of insolation. Many of the stones are highly polished as a result in part from the attrition of dust and sand blown by the wind, and in part from a coating on their surfaces of a glaze caused by the evaporation of siliceous and ferruginous water on the stones. This desert glaze, or varnish, Jack states is a feature common to arid regions. Largely because of the reflection of light from their polished surfaces, but also because of their presence under foot, the gibber plains present difficulties for the traveler. For example, Spen- cer and Gillen (1912: 40) narrate: “A little way to the north of Oodnadatta we passed on to gently undulating country, with low-lying, flat-topped hills and remarkable plains covered with small stones. Nothing could possibly be more desolate than these ‘gibber fields.’ * * * The horizon is shimmering and indistinct and the level ground is covered with a layer of close-set, purple-brown stones, all made smooth and shiny by the constant wearing action of wind-borne sand grains, for, in winter especially, a strong southeast wind often blows all day long.” As these excerpts would indicate, the desert sandstone plateau con- stitutes, for various reasons, a feature of the landscape of the more arid portion of South Australia that is striking in the extreme. The mountains and the hill country of South Australia are of two classes, geologically unlike and to a degree constituting separate physio- ARID PORTIONS OF SOUTH AUSTRALIA. 37 graphic areas. Of these, the more ancient, Archean, make up the large and relatively high upland area in the extreme northwest portion of the state, where are the Musgrave Ranges and others. Remnants of for- mer extensive mountain ranges, similar ancient rocks, occur south of Oodnadatta, and as isolated hills and low ranges to the west of the great valley of South Australia. Of these, the chief may be said to be constituted by the Gawler Range, and among the isolated hills, those at Tarcoola and Wynbring. In addition, portions of the Flinders Mountains, including parts of Mount Lofty Ranges near Adelaide, belong to the ancient pre-Cambrian mountain system. In the region west of the great valley the elevations of such rocks are for the most part inconsiderable. It is the waste of the ancient granitic rocks, which, according to Howchin (1909: 67), has supplied the sand in the region to the north of the Great Bight. The elevation of the ranges referred to as being in the northwestern portion of the state is very considerable, reaching an altitude of 5,200 feet, which is the great- est altitude in South Australia. - But the greatest area of highlands in South Australia.is made up of.a - hilly or mountainous central region which extends from the southern ocean dué north to Maree (Hergott Springs), approximately 500 miles. This elevated region may perhaps be regarded as a peneplain which has become much worn down and much dissected by streams. It con- stitutes one gepgraphical unit. In the northern portions the mountains bear the stamp of an arid climate, but in the south the outlines are rounded from the accumulation of soil and are well covered with vege- tation. Following Howchin, we can for convenience separate the Central Highlands into three groups. Of these, the southernmost is made up very largely of the ranges which together constitute the Mount Lofty _ system. These attain an extreme altitude of 2,334 feet (Mount Lofty). The middle section is made up of peneplains and rugged hills, the highest of which (Mount Bryan) is 3,065 feet. The general direction of the mountains of the Central Highlandsis north-south. They are separated from one another by the undulating plains, peneplains, which, in the middle section, along the line of the railway at least, do not attain a greater altitude than 2,000 feet above the sea (Howchin and Gregory, l. c., 86). The middle section joins the southern end of the Flinders -Mountains. Extending as it does north to Maree (Hergott Springs) and east to Lake Fromme, the Flinders Range constitutes by far the largest portion of the Central Highlands. In the region of Port Au- gusta-Quorn the mountains attain an altitude of 3,174 feet (Mount Remarkable), with Mount Brown and Devil’s Peak, near Quorn, slightly less. Mount Arden, about 10 miles north of Quorn, is one of the lower summits. On its way north the railway parallels the eastern shore of Lake Tor- 38 PLANT HABITS AND HABITATS IN THE rens, and for much of the way skirts the western base of the Flinders. As seen from the railway line, the mountains rise fairly abruptly from the plain. This is due, according to Howchin, to faulting connected with the formation of the great central valley of South Australia. Near Beltana the line enters the hills and at Copley (Leigh’s Creek) it runs in the valley separating the smaller western range from the main ranges to the east. The highest altitude given by Howchin of the northern Flinders is 3,120 feet (Freeling Heights), and among the prominent elevations is Mount Serle, east of Copley, to which refer-. ence will be made later. It has already been mentioned that in the north the Central Highlands assume the rugged appearance character- istic of mountains in an arid land. This implies also the presence of canyons cut deep by water-courses. Such stream-beds are dry, how- ever, a large part of the year. For the most part the Central Highlands are of lower Paleozoic (Cambrian) age. The exceptions to this have already been referred to. There are occasional structures which are of great interest to the geolo- gist, as, for example, the circumclinal fault known as Wilpena Pound, where a great basin was formed, access to which can be had at one * point only, and the glacial “till,” supposedly pre-Cambrian, which can be seen at Depot Flat, near Quorn, as well as at other places. From the present standpoint the leading interest in the highlands of South Australia lies in their effect on the climate. [he isohyets and isotherms are pushed considerably northward by the central land elevations and with this, and because of it, an extra-regional distribution of plants occurs by which those of the cooler and more moist south are projected far north, into the midst of a region that is remarkably hot and dry. The lowlands of South Australia may be said to consist mainly of the basins, great and small, in which the lakes in the northern portion of the state more especially are situated, and, in addition, the region along the course of the Murray River. They are the Lake Eyre Basin, that of Lake Fromme, Lake Torrens, and Lake Gairdner. In addi- tion are the coastal plains, of which the one between Port Augusta and Port Pirie needs only be mentioned. The positions of these basins are given in figure 10. The Lake Eyre Basin is a part of the great artesian basin of central Australia, which is estimated by Taylor (1914:108) to have an area of 576,000 square miles. Only a relatively small proportion of the total, however, is in South Australia. The deepest portion of the basin centers in Lake Eyre, the bottom of which is estimated to be 60 feet below the level of the sea. Where the railway crosses the southern extremity of the lake the altitude is 3 feet below the sea. The basin is a closed one, but the evaporation-rate is so great that much of the area which constitutes the lake is dry most of the time, being covered by ARID PORTIONS OF SOUTH AUSTRALIA. 39 water only at times of flood. In the south arm, however, the lake usually contains salt water. Important streams enter Lake Eyre on the east, west, and north, of which the Barcoo, or Cooper’s Creek, is the most important. On the western side is Neales River, near which Oodnadatta is situated, and which is in part a broad and poorly defined drainage channel, which carries water but rarely. Howchin remarks that the opinion formerly held, that the seq had but lately retired from this vast country, is not correct. Rather at a remote time, the Cretaceous, the sea extended from the north as a great gulf, or sea, and covered most of central Australia. Probably there never was a continuous connection, north to south, between what is now Spencer Gulf and the Gulf of Carpentaria. The lowest portion of the land connection between the two is at present given as being 175 feet above the sea. The depression in the southern portion of the Great Basin is thought to have been brought about through a secondary subsidence affecting this portion only. The desert sandstone, as remarked above, was laid down in Upper Cretaceous time, during a period of elevation when the basin was a fresh-water lake. At this time the rainfall was probably better than now and the climate cooler. The surface features of the Lake Eyre Basin, and these are repre- sentative of the entire region, are of three kinds, according to Howchin and Gregory. These are tablelands, which, as seen in the vicinity of Oodnadatta, are generally of relatively small extent: (1) “‘buttes” in fact, (2) stony deserts which are constituted by the ‘‘gibber” plains, and (8) the sandhills. At Oodnadatta, also, the surface (except the tops of the buttes) is covered by small stones of various sizes and shapes. The “‘gibbers”’ are usually flattened, polished, and of a reddish-brown color. From the fact that the stones fit together closely, they are probably important in conserving whatever water may fall by cutting down evaporation from the surface of the soil. Just about Lake Eyre, on all sides, sandhills are plentiful; in general, these constitute an important feature of the surface topography in the northern part of South Australia. The sandhills occur as ridges, usually not of great height, and run in a generally northeast and southwest direction. They are frequently separated by ‘‘clay-pans,” a quarter of a mile or more in diameter, which hold water for a period after rains. Like the “‘gib- bers,” the sand is derived from the eroded desert sandstone. As Howchin points out, owing to there being no opportunity for carry- ing away the sand, as by water-currents of whatever kind, it remains in the basin, dr ifting here and there through the action of winds, and “with the ever-accumulating products of waste, the highest hills are gradually covered by drift and the country is ultimately buried under its own ruins”? (Howchin and Gregory, 1909:103). 40 PLANT HABITS AND HABITATS IN THE A striking and characteristic feature of the Lake Eyre Basin as a whole is the fact that it is an important part of the vast artesian basin of Australia, of which approximately one-fifth lies in South Australia. There are numerous “‘mound”’ springs on the border of Lake Eyre and many deep borings have been made, some of which yield great quantities of water. The one at Coward Springs, for example, has a daily flow of 1,000,000 gallons. The water-supply is derived from the western flanks of the mountains of New South Wales and Queensland and the intake is chiefly porous sandstones, probably of different geo- logical ages. These sandstones are covered by great thicknesses of dark-blue shale, sandstones, and impure limestones of Cretaceous age. Thus the subterranean water is far too deep to be of direct benefit to surface plants, if it were always of suitable quality, which is sometimes not the case. To the southeast of Lake Eyre is situated a chain of lakes, of which Lake Fromme is the largest. These are described by Howchin as being merely extensive flats which are sheets of water after heavy rains and are saline wastes during dry seasons. They are the centers of a relatively restricted drainage area, and no rivers of importance dis- charge into them. Another group of related basins, somewhat larger than those of the Fromme group, lies to the west of Lake Torrens and north of the Gawler Ranges. Of these, the largest is Lake Gairdner. The Trans- Australian Railway skirts the northern portion of these basins. Tarcoola is a few miles west of them and Port Augusta is 50 miles, more or less, to the east. Lake Gairdner and the rest of the basins lie at the northeastern side of scattered remains of mountains of Archean age, from the waste of which the sand of the region may have been derived. The region is relatively very dry. The 10-inch isohyet which, in passing through the Flinders Mountains, curves rapidly to the north, is here deflected as strongly to the south and includes none of the area. The northern section of the Flinders Mountains has on the west the central rift-valley of South Australia, which is made up of Lake Torrens on the north and a descending series of flats and lagoons which connects it on the south with Spencer’s Gulf. Thus Lake Torrens, which owes its existence to faulting, is in a manner distinct in origin from the other basins. The bold western side of the Flinders Mountains has already been noted. This is the upthrow side of the north-south fault by which the Great Valley of South Australia was formed. This fault, as Howchin states, increases in importance as it goes south and includes Gulfs Spencer and St. Vincent (see also Taylor, 1918:97). The area of depression, therefore, fairly parallels the western side of the entire central mountain system of South Australia. That the earth’s crust in this region is not in equilibrium is further evidenced by the occurrence of earthquakes from time to time center- ARID PORTIONS OF SOUTH AUSTRALIA. 41 ing along some portion of the rift valley. No important rivers empty into Lake Torrens and what water it holds is derived directly from such rains as fall on its surface. It is well without the 10-inch isohyet, the average rainfall of the basin being probably but little over 6 inches. Figure 13 (Taylor, 1. c.) gives concisely the main points in the geo- logical history of the rift valley of the central portion of the state. As Taylor explains, in “A” is given a hypothetical diagram showing how in former ages there was a well-developed and centrally situated drainage system which led from the Barkly tableland on the north down to Jeffrey’s Deep. The general course of the valleys is north and south. The Central Highlands, comprised by the Flinders and adjoining ranges, have not yet been formed. In “B” important alterations are seen to have taken place. The sea has encroached on the land to the south, advancing up the basin of the Murray River. In the mean- time, epeirogenic movements have raised an elongated plateau in the south, and this has affected all of the river courses, in places blocking them and bringing about the formation of lakes. We thus see the origin of all of the leading lakes and basins. In “C’’ the western por- tion of the uplift is seen to have slipped in, forming Spencer’s Gulf and Gulf St. Vincent. The MacDonnell Ranges (Northern Territory) have arisen and the Lake Eyre Basin has sunk away from the earlier grade. The early river system may possibly date back as far as the Cretaceous, when a vast sea covered the western portion of Queensland. It seems certain that in the early geologic times the rainfall was heavy in central and northern South Australia and in central Australia. Taylor suggests that the heavy rainfall in the past may have been due to the presence of great arms of the sea to the east, such as the Tertiary sea at the mouth of the Murray. The Murray-Darling lowlands are very extensive. Taylor esti- mates the area to be an approximate square of about 400 miles on each side. Of these only a small portion is included within the state of South Australia, and it is wholly comprised of the ancient Murray estuary or bay, into which, in earlier geologic times, the Darling and the Murrumbdigee, as well as the Murray, emptied by separate mouths. The ancient estuary is for the most part flat, except an area in the southeast, where there are sandhills only a few feet above the sea. According to Howchin, for example, at the point where the River Murray enters the state, its summer level is but 57 feet above sea-level. At Morgan it is only 5 feet 4 inches, which gives a gradient of the river of only 0.5 inch to the mile. The banks of the river at Blanchtown are approximately 150 feet higher than the level of the stream at low water. As one overlooks the area from the mountains to the west, where the view isvery extensive, it is unrelieved by any eminences whatever. This flatness, together with the blueness of the distant mallee forests, gives the impression that one is looking over the sea. 42 PLANT HABITS AND HABITATS IN THE The most interesting feature of the country is the River Murray. The Murray and its tributaries drain the western slopes of mountainous eastern and central Queensland, New South Wales, and Victoria. In favorable seasons, with its main tributary, the Darling, it can be navigated for 2,000 miles. At Blanchtown at high-water (as in October 1918) the river is approximately 600 feet wide. The vertical variation between the summer level of the river and the winter-flood level is 20 feet or more. In the area considered it does not overflow its banks and it has no direct and immediate effect on the native flora along its shores. LIMATE. TEMPERATURE. South Australia enjoys a mild temperate climate. The lowest emperature recorded up to 1912 was at Mount Barker, 24.3° F., and the highest recorded shade temperature was 119° F. at William Creek, in the far north, about midway between Maree (Hergott Springs) and Oodnadatta. The former is near the southern termination of the Central Highlands and the latter is in the Lake Eyre Basin. Except in the more arid districts the seasonal and the diurnal variations are not extreme. The 65° F. isotherm enters the state slightly south of the center of the eastern border, curves to the north in crossing the Central Highlands, dips south in the Lake Gairdner Basin, and, taking a northwestern direction, reaches the highlands in the extreme northwestern portion of the state. Here it is again deflected sharply north and leaves the state not far from the northwestern corner. About 64 per cent of the entire area of South Australia is within the 65° to 75° F. isotherms. The really great difference in the apparent amount of heat received by the northern and mainly arid (as contrasted to the southern and mainly humid) portions of the state is further suggested by the number of days in each in which the thermometer registers a shade temperature of 90° F. or more. At William Creek, for example, there are on the average 114 days in each year when the thermometer registers 4 temperature of 90° F. or over, while, on the other hand, at Adelaide, which is by no means the coolest southern station, the number of days in which the thermometer shows this temperature is only 43 in the year. This may not mean, however, that there is a corresponding difference in the amount of heat units actually received between the two stations, since there are nearly three times as many nights, 40 as against 14, during which the thermometer records a temperature of 40° F. or less at William Creek, as opposed to night temperature at Adelaide. Here again the temperature at Adelaide probably does not represent the extreme condition, but reveals the steadying in- fluence of the Southern Ocean, near which the city is situated. ARID PORTIONS OF SOUTH AUSTRALIA. 43