v] FERNS 85 



too imperfect to be determined with any degree of 

 certaint}^ We have, however, satisfactory grounds 

 for the assertion that the Juan Fernandez fern 

 affords a striking confirmation of the truth of 

 Darwin's dictum that 'Rarity, as geology tells us, 

 is the precursor to extinction.' In this remote oceanic 

 island, for reasons which we cannot explain, there 

 lingers an isolated type which belongs to another age. 

 The following passage, which forms a fitting 

 introduction to an account of two other genera of 

 ancient ferns, is taken from a description of an 

 ascent of Mount Ophir in the Malay Peninsula by Dr 

 A. R. Wallace in his well-known book on the Malay 

 Archipelago : — ' After passing a little tangled jungle 

 and swampy thickets, we emerged into a fine lofty 

 forest.... We ascended steadily up a moderate slope 

 for several miles, having a deep ravine on the 

 left. We then had a level plateau or shoulder to 

 cross, after which the ascent was steeper and the 

 forest denser till we came out upon the Padang- 

 Batu, or stone-field.... We found it to be a steep 

 slope of even rock, extending along the mountain 

 side farther than we could see. Parts of it were 

 quite bare, but where it was cracked and fissured 

 there grew a most luxuriant vegetation, among which 

 the pitcher plants were the most remarkable.... A few 

 coniferae of the genus Dacrydium here first appeared, 

 and in the thickets, just above the rocky surface, 



