44 A CONTEIBUTIOX TO, ETC. 



making their systematic arrangement depend principally on the 

 iudusium and the ring of the sporangium ; whilst others believing 

 that in some species the indusium is very variable, and that too 

 much attention to the obliquity of thering must separate the 

 closest allies, rely upon the venation and the rhizoma (or pros- 

 trate rooting stem) as the most valuable points for distinction. 

 With regard to the latter, it is affirmed by one of the most dis- 

 tinguished Cryptogamic Botanists of the day, that "venation 

 though, evidently of great importance, froni its close connection 

 with the fruit, is too subject to variation to afford incontestable 

 general characters, however valuable it may be in particular in- 

 stances ;" and further, with respect to the different forms of 

 Bhizoma, he " doubts very much whether any particular type 

 of formation attends the rejection or retention of the stipes." 

 When reading such opinions as these, one is almost inclined to 

 join in the humble wish of Cicero, " Utinam tarn facile possem 

 vera invenire, quam falsa convincere ;" but the fact is, that al- 

 though no arrangement of sub-orders or genera can as yet be de- 

 vised, which is not exposed to objection, yet as our knowledge 

 advances, many points which are now deemed obscure will be 

 cleared up, and a more extended range of observation will reveal 

 the exact amount of importance which should be attached to 

 each organ. 



The splendid work of Sir William Hooker, when compared 

 with those of previous cryptogamic writers, is a wonderful evi- 

 dence of the progress of science, and displays not merely an im- 

 mense knowledge of species existing in all parts of the globe, but 

 also a profound attention to the characters by .which any sound 

 philosophical classification must be regulated. Following in the 

 steps of the illustrious Robert Brown, to whom the work was 

 originally dedicated (1846), and of whom he says: "Had he 

 given his master-mind to the complete development of this sub- 

 ject, little would have remained to his successor but to tread 

 closely in his steps," the distinguished author has furnished a 

 systematic arrangement which will not only assist in the classifi- 

 cation of Australian ferns, but those of the whole world. Taking 

 a wise and middle course " between the highly multiplied dis- 

 tinctions of Dr. Presl and Mr. John Smith, and the meagre 

 enumerations of Wildenow, Sprengel, Link, Kunze, and others," 



