PREFACE. IX 



Fems. Tliis is owing to three causes. 1. The difficulty 

 of accurately defining in words the highly varied forms of 

 these beautiful plants. 2. The often imperfect or incom- 

 plete specimens collected, especially of the larger kinds. 

 And 3. A too generally received opinion that the same 

 Fern is not likely to grow in two very remote portions of 

 the globe. In illustration of the last of these remarks, a 

 more striking instance can hardly be adduced than the 

 universally known Osmunda regalis of Linnaeus, which, 

 retaining its own name as an European species, has been 

 described as O. upectahilis in North America, O. speciosa 

 in Nepal, and O. Leschenaullii in the Neelgherries. 



Innumerable examples of a similar kind might be 

 brought forward, and nothing can assist in rectifying these 

 errors but the opportunity of examining a large number of 

 .specimens from various habitats. The want of such op- 

 portunities has led botanists of high repute not uncom- 

 monly to counnit mistakes ; and the author will take the 

 liberty of adducing one or two instances which have re- 

 cently come before him ; in fact, so recently, that it was 

 only just as the concluding sheets of the present volume 

 were in the press, lie would not otherwise have failed to 

 notice some of the errors before. 



While engaged on the genus Cystopteris, he received 

 the No. of Jacquemont's ' Voyage aux Indes Oricntales, 



