360 IMPROVEMENT IN THE ARRANGEMENT OF FERN&. 



fertilized, remained to our own times a great mystery j and even 

 respecting the accompaniments and special arrangements of these 

 essential parts, the progress of correct observation was very gradual- 

 The first attempts at forming generic groups were founded only on the 

 general figure of the frond, which never could afford any good results, 

 since we have closely resembling forms of which the fructification is 

 entirely diff"erent, and there can be no question which circumstance is 

 most important. Linnssus introduced as a character the shape and 

 position of the heaps or bundles of capsules (now named sporangia)^ 

 to which heaps the name sorl is assigned. Sir James Edward Smith 

 added the consideration of the membranous cover (called the induskim) 

 raised from the surface of the frond, folded back from its edge, or 

 expanded at the termination of a vein, and where it occurs protecting 

 the cluster of sporangia, whilst it has remarkable variations in figure,, 

 mode of attachment, and position in regard to the sorus. The 

 importance of this character has led to many applications of it which 

 improved observation has justified. Kobert Brown first employed th& 

 venation of the frond, though using it rather for sectional divisions 

 than for genera. Presl, and John Smith of Kew, have worked up this 

 subject fully, making it a foundation for genera, which have been 

 extensively adopted by recent writers, though Sir W. J . Hooker, in his 

 great work, the Species J^ilicum, abandons many of them, and receives 

 others only as sectional divisions. He had previously, in the " Genera 

 of Ferns," in publishing the admirable microscopic drawings of Francis 

 Bauer, with many valuable additions, given the characters of many 

 new genera of Brown, J. Smith, Mayer, Presl, &c., without otherwise 

 indicating his opinion than by a caution in the preface against his being 

 supposed to adopt them all; but when he applied himself to his great 

 work on the species, he was led to admit venation only as a character 

 of subgenera or sections. His judgment has great weight, yet it must 

 be acknowledged that the venation affords a striking, intelligible and 

 convenient character, affording very natural sub-divisions; and if any 

 should think that its use for distinguishing genera is inconsistent with 

 the botanical rule that such distinctions must be drawn from the parts 

 of fructification, let him recollect that the whole frond is a secondary 

 growth, devoted to the reproductive function, in which vascular tissue, 

 which had no existence in the primary plant, is introduced, and is so 

 intimately connected with the production of the sporangia that it may 

 well be accounted a part of the system of fructification requiring to be 



