10 GENERAL REMARKS ON THE 



account ; for at the southern extremity of Van Diemen's 

 Island, where the necessary conditions exist, the relative 

 proportion of Cryptogamous plants is not materially different 

 from that of the south of Europe. 



In that which I have called the principal parallel of New 

 Holland, however, Cryptogamous plants appear to be much. 

 less numerous than in the corresponding latitudes of the 

 northern hemisphere ; and within the tropic they probably 

 do not form more than one twelfth of the whole number of 

 species. 



In several' of the islands of the Gulf of Carpentaria, 

 having a Plora of Phsenogamous plants exceeding 200 

 species, I did not observe a single species of Moss. 



From the three primary classes of plants already treated 

 of I proceed at once to those groups called Natural 

 Orders or Families ; for the intermediate divisions are too 

 much at variance with the natural series to be made the 

 subject of such general remarks as have been already offered 

 on the primary classes, and which are equally admissible 

 with respect to the natural families. 



A methodical, and at the same time a natural, arrange- 

 ment of these families is, in the existing state of our know- 

 ledge, perhaps impracticable. It would probably facilitate 

 its future attainment, if at present, entirely neglecting it, 

 attention were turned to the combination of these orders 

 into Classes equally natural, and which, on a thorough in- 

 vestigation, might equally admit of being defined. The 

 existence of certain natural classes is already acknowledged, 

 and I have, in treating of the Australian natural families, 

 ventured to propose a few that are perhaps less obvious, 

 stih more, however, might have been suggested had this been 

 the place for pursuing the subject. 



640] The natural orders in the Genera Plantarum of Jussieu 

 are exactly 100; subsequent observations of Jussie a him- 

 self and of other botanists have considerably increased their 

 numbers, so that in the lately published Theorie Elementaire 

 de la Botanique of Decandolle they amount to 145. 



The plants of Terra Australis are referable to 120 



