60 DUBLIN NAXmiAL HISTORY SOCIETr. 



collection both of growing plants and dried specimens in the possession of G. B. 

 Wollaston, Esq. This has enabled me to add several species and even genera 

 to the two divisions treated of at our last meeting. The genera are Cystopteris 

 and Adiantum, to the sub-var. Multifidum (including under them three species), 

 to which Hymenophyllum Wilsoni is also added by him. To the number of spe- 

 cies in the variety Cristatum I have not obtained any additions ; but in his col- 

 lection maybe found a most perfect series of forms illustrative of this monstro- 

 sity, and well worthy of study, exemplifying in a beautiful manner every grada- 

 tion of it in almost all the organs of the plant, from the mere simple renate di- 

 vision of the frond, up to the extreme forms of division recorded on the last day. 

 To-night I propose to conclude the subject, by considering the analogies of the 

 remaining abnormal forms of Filices. 



Since I first attempted this arrangement, so many additional species of these 

 have been brought forward, that without any difficulty we can accomplish a di- 

 vision only hinted at then — viz., separate them into four classes — i. e., two va- 

 rieties and two sub-varieties, instead of one of each. Vide pp. 47, &c. For 

 these I intend to suggest new names, as there were many objections to 

 the names then used. The first, comprised under my old name Cambri- 

 cum, I mean to call Dissectum, the sub-variety I call Sinuatum still, but limit 

 its definition. — Dissectum variety — frond generally more developed than nor- 

 mal ; edges, both primary and secondary, crenately or irregularly lobed and 

 symmetrical ; segments rounded at ends ; their edges curled, and crisped, and 

 confluent; generally barren ; nervures terminating within leafy expansion, and 

 distinct throughout their whole course. Examples — As : Trichomanes, var. inci- 

 sum ; Cten. vulgare, var. Cambricum (Linn.). (This division includes so much 

 of my variety Cambricum as had the parts of the plant in excess.) Sinuatum, 

 sub-var. — frond mostly more luxuriant than normal ; segments irregularly 

 lobed and serrated, pointed, and distinct, generally unsymmetrical ; outline 

 pointed and distinct ; fruitful ; nervures terminating within leafy expansion. 

 Examples — As: Trichomanes, sub-var. Sinuatum (Mei) ; Cten. vulgare, var. Hi- 

 bernicum or Mackayi (auct.). These forms are essentially modifications of a 

 secondary axis (generally the veins and venules, which we find multiplied and 

 divided, but not symmetrically as a whole), and consists in the excessive 

 unsymmetrical development of some one or other. It is often difficult to 

 separate this variety from the variety Cristatum, especially in simple fronds ; 

 but we have a valuable guide in one character, which prevails almost through 

 the entire — the barrenness of the frond — a character so universal in the class, it 

 might almost be adopted as distinctive. In some species this may be explained 

 by the modification the veins undergo, the vein, which should be merely forked 

 and bear the spore case, becoming branched and barren, as is seen in Ctenop- 

 teris vulgare. The number of species in which it is found is rather limited, 

 though, doubtless, if investigation be made, others will turn up. The sub-va- 

 riety is fertile, the same modification not taking place in the venation. There 

 is a great latitude of modifications in the forms composed under Sinuatum, from 

 the simple irregularly crenate frond up to divisions as well marked as those with 

 which you are familiar in the Polypodium cambricum of Linnaeus. Under this 

 group we find an illustration of a previous observation, that a sub- variety and 

 a variety are sometimes found in accidental combination, — with this limit, that, 

 as far as I know, the parallel sub-groups are never found so. For example, you 

 will find variety Dissectum in combination with sub-variety Multifidum, but 

 never Dissectum in combination with Sinuatum cristatum in combination with 

 Multifidum. How far varieties combine with one another, I am not prepared to 

 state.* The next sub-group comprises the latter portion of my old Cambricum, 



• The varieties are found combined with one another. The following are examples':— Vara. 

 Cristatum and Laciniatum, in Ath. Filix Fsemlna, R. Gunning's variety. The same vars. in Phyl. sco- 

 lopendrium, Guernsey form : but vide list. Sub-varieties obey tlie same law— ex. gr., Lophodium 

 Filix mas. Ramosum (Wol.) is sub-var. multifidum combined with sub-var. sinuatum, <fcc. The fol - 

 lowing remarlcB were made at the meeting held in June, 1854 :— In the paper read by me at at our last 



