ON THE NOKTH-AUSTEALIAN EXPEDITION. 189 



plants constituting the polypetalous orders, we are, at least as 

 regards Australia, but scantily acquainted with this section of the 

 vegetable kingdom ; and if, therefore, many plants noticed during 

 the expedition are on this occasion pronounced as additional to 

 the Australian flora, it is to be admitted, that some of them in all 

 probability occur already in the collections of Allan Cunningham, 

 of E. Brown, or even of Banks and Solander, still unrevealed 

 to botanical science. 



The number of plants observed in the whole extent of our 

 journey amounts to nearly 2000 species, which exhibit the pro- 

 portionately great number of 160 natural orders, and more than 800 

 genera. Monocotyledonese bear to Dicotyledonous plants scarcely 

 the proportion of 1 : 4, and Acotyledonese (exclusive of minute 

 fungi) 1 : 8, but with the omission of Algae only 1 : 12. In North, 

 North-western, and Central Australia cryptogamic plants diminish 

 in number with the decrease of atmospherical humidity to such an 

 extent, that their relative proportions to the rest of the vegetation 

 is probably much smaller than in any other part of the globe, 

 mosses and lichens being almost entirely excluded from many 

 extensive tracts of the country. 



The richest natural orders of plants observed in tropical Au- 

 stralia may be arranged according to the preponderance of species 

 in the following series : viz. LegwninoscB, Myrtacece, Composites, 

 Cyperoidece, Algae, EtipJiorhiacecd, Mubiacece, Filices, FroteacecG, 

 Malvacecd, Goodeniacece, Solanacew, Convolvulacece, Sapindacece, 

 ScrophularincB, &c. But this series, applying to the accumulation 

 of plants from all the country traversed, has to receive consi- 

 derable alteration in adapting it exclusively to the north-west 

 portion of the continent, where Composited, Euphorhiacece, Mubi- 

 acecB, and Filices exist only in a much diminished proportion. 



The expedition has not disclosed a single new fundamental 

 form of the vegetable kingdom in the type of a new natural order, 

 unless such should be exhibited yet by any of those, which were 

 seen in a state too imperfect for accurate classification, and were 

 consequently excluded from the appended systematical list. But 

 HippocratecG, Alangiacece, Hydrophyllece, EpJiedrecd, and Ponte- 

 deriacece are now for the first time introduced into the Australian 

 flora. The genera, richest of all, are to be arrayed according to 

 their predominance in the following succession : — Acacia, Euca- 

 lyptus, Solanum, Panicum, Fimhristylis, Orevillea, Goodenia, Hi- 

 biscus, Ipoiuoea, Stylidium, Mitrasacme, Andropogon^ Gyperus, 

 Sida, Crotalaria, Indigofera, Loranthus, Ficus, &c. 



