112 



Art. XL. — Proceedings of Societies. 



LINNEAN SOCIETY. 



November 2, 1841.— The lord Bishop of Norwich, President, in the chair. The following donations were 

 announced. Nearly 1000 species of plants collected in Riakhy, Piauhy and Goyaz, by Mr. Gardner. Spe- 

 cimens of Gnaphalium margaritaceum and of a peculiar form of Linaria repens from the west of Ireland, by 

 Mr. Hinckes. A collection of dried plants fi-om the West Indies and Madeira, by Lord Dartmouth. Mr. 

 Ingpen exhibited a myrtle growing in a glass cylinder carefully sealed. A letter from M. Alphonse De- 

 Candolle, announcing the death of his father, was read. 



BOTANICAL SOCIETY OF LONDON. 



November 5.— Hewett Cottrell Watson, Esq., F.L.S., Vice-President, in the Chair, Donations to the li- 

 brary were announced from the Botanical Society of Edinburgh, the West Riding Geological Society, the 

 Portsmoufli Philosophical Society, the Lancaster Natural-History Society, Mr. Thwaites, Mr. Lees and The 

 Kev. I. Sansom. Mr. G. Knapp presented some grasses and mosses from Ternando Po ; and British plants 

 ■were announced as having been received from Mr. Thwaites, Mr. Croall, Mr. Brown, Mr. Fordham, Mr. 

 Simpson, Mr. Lees and Mr. Bidwell. Mr. H. O. Stephens of Bristol presented thirty-three species of British 

 Fungi. 



A paper was read from Mr. G. H. K. Thwaites, on Polystichum amleatum and Pol. lobatum. The 

 author observes that owing to the difference of opinion entertained respecting these ferns by botanists of ce- 

 lebrity — some considering them two distinct species, and others that they are merely varieties of one — any 

 facts tending to bring to light their real character must be interesting ; and therefore he has much gratifica- 

 tion in making known a peculiarity of structure exhibited by each, whereby he considers all doubt as to their 

 being distinct species will be removed. 



The two ferns, in their typical form, differ very materially from each other; and their differences have 

 been well described by those who have written on the subject. But almost all, if not the whole of the char- 

 acters which have been set down as distinctive, are liable to be so extremely modified by different degrees of 

 altitude, moisture, light, exposure &c. of situation, that an unpractised eye would often be quite unable to de- 

 termine the species of these closely-allied plants, whence, questionless, has arisen the doubt as to their sepa- 

 rate specific individuality. Thus, Polystichum lobatum, upon an elevated situation, possesses a lanceolate 

 frond, generally very close and compact ; its pinnae overlapping each other ; occasionally, however, these are 

 distant from each other to almost the extent of their width, and the pinnulee are more separated, so that the 

 plant much resembles P. aculeatum. But P. lobatum, when gi-owing in a low situation, is still more like P. 

 aculeatum ; its fronds, instead of being lanceolate, inclining more to ovate, its pinnulee also are not merely 

 serrated, but become slightly pinnatifld, indeed the plant can with difficulty be identified. These facts, and 

 several others which might be adduced, show the slight value, in this genus, of characters derived from the 

 outline of the frond or of the pinnse and pinnulse, which are all so liable to vary in this particular: it was 

 therefore very desirable to endeavour to find some more constant character by which these kindred species, if 

 they proved species, might be distinguished one from the other ; and after many hours spent in diligent exa- 

 mination of a gi-eat number of fronds, the author discovered a difference of venation in the two species, which 

 he thus describes. 



" In examining the fronds of P. aculeatum, it may be noticed that the veins which bear thecae are not 

 continued, like the rest of the veins, to the edge of the pinnulse, but each terminates either at its mass of the- 

 cae, or at a very little distance beyond it. The same thing is not observable in P. lobatum (when mature), for 

 the corresponding veins in this are each continued through its mass of thecae to the very edge of the pinnule, 

 and even in the fronds of immatm-e plants of this species, when there is but little fructification, the same cha^ 

 racter is perceptible in the pinnulae nearest the base of the pinnae and of the frond — the parts which in ferns 

 exhibit most strikingly all the charactei-s of maturity : in a few of the terminal pinnulae some of these veins 

 do not reach the edge. It must not be concealed that in P. aculeatum, in an extremely few instances (being 

 just what might be expected) is a slight indication discoverable of a theciferous vein being continued to the 

 edge of the pinnule ; but in this the appearance is very different to the decided character observable in P. lo- 

 batum."— (?. E. D. 



