REMARKS ON BRITISH FERNS. 81 



appear firm. As the roots emerge, they readily reach the soil, 

 which circumstance I think is more conducive to their safety, than 

 the removal would be from a bed of pure sand into separate pots 

 of soil. If these few loose hints — for such only they are, — lead 

 to any enquiry, I shall be happy to furnish every kind of infor- 

 mation within my power. G. I. T. 

 January 13, 1834. 



ARTICLE III. — Remarks on Sir J. E. Small's Arrange- 

 ment of the British Ferns— No. III. By M. 



The genera of Dorsal Ferns, or those which have their fructifi- 

 cation on the under side of the leaf or frond, have been founded 

 upon different characteristics by different writers. 



Ray, and some other systematic botanists, resorted in the first 

 instance to the shape of the frond ; but this is so similar in many 

 of the species, that it is useless, alone, as a genuine distinction. 



Lin.veus depended upon the shape of the sori, or masses of 

 capsules ; whether round, oblong, linear, &c. This forms a much 

 better distinction, but still is insufficient. 



Sir J. E. Smith, who purchased the Herbarium of Linnaeus, 

 and was thus furnished with a vast collection of specimens of 

 l'< in-, first suggested an additional principle of arrangement, 

 ■rising from the form and insertion of the membrane which in 

 most of the Ferns protects the masses of capsules, and especially 

 from the manner in which this cover bursts when the capsules 

 beeomeripe. This is found to afford very certain distinctions ; 

 to establish the most natural genera ; and greatly to facilitate their 

 in\«vii'_',ition. 



The numerous species formerly included in the genus Polypo- 

 diinn, are by ihis means divided into three genera — Polypodium, 



ptdinm, and Crates. 



I'olvjM.dimii contains four species, which have no cover to the 

 ■ ■I capsules* 



As].i(liiiiu — Shield Fern, thirteen species ; which have a cover 

 l\ orbicular, fixed by the centre, and when ripe separating all 

 round. 



1 Bladder Fern. This is a name given by Smith to a 



delicate little tribe, distinguish, d from either of the others by the 

 Vol. II. M 



