280 



median longitudinal sectional views of the same. Tn all these it will 

 be seen, that the foliaceous part is bent forward on the stipes, forming 

 therewith a kind of hook ; a structure strikingly different from that 

 of Pteris tremula, represented at figs. 8, 9, 10, which, although gene- 

 rally held to be closely allied to aquilina, very clearly exhibits the 

 usual circinate vernation. It may, however, be observed, that the ex- 

 treme point of the bent rhizoma has a slight tendency to exhibit a 

 curve, as shown in fig. 7, and all the partial rachides are more or less 

 circinate, as shown at b in fig. 1. There is something very anoma- 

 lous in the rapid development of the foliaceous portion of the frond : 

 at a stage, as regards the stipes, when the circinate frond of multiflora 

 exhibits, if unrolled, all its pinnae and pinnules, and even clusters of 

 capsules, that of aquilina is a mere indication, a slight inequality on 

 the surface, and its component parts cannot be detected under a lens 

 of high power : yet in a few days we find it has increased and un- 

 folded with such marvellous rapidity, that in aquilina we have a frond 

 surpassing that of nearly every other British fern in magnitude. 

 The texture of the frond,* when the plant has grown in its naturally 

 exposed situation, is tough and somewhat leathery : in the autumn it 

 assumes a brown hue, and becomes still more rigid and coriaceous. 

 When growing in shade, as in woods, this texture is not so observable. 

 The lobes or ultimate divisions of the frond have a median vein, «, 

 fif^. 11, and many branched lateral veins, all of which run to the ex- 

 treme margin and there unite with a marginal vein, h b. The margin is 

 convolute, and its elasticity is so invincible that it is ex- 

 tremely difficult to maintain a lobe in a sufficiently flat 

 position to exhibit, as in the accompanying diagram, 

 the formula of venation. Attached to the marginal 

 vein and extending throughout its length, is a bleached 

 semi-hyaline membrane fringed with a series of jointed 

 capillary segments.f Beneath this membrane are the 

 capsules, also attached to the marginal vein, and ar- 

 ranged along it in a continuous linear series. Again, 

 beneath this linear series of capsules is a second bleach- 

 ed and fringed membrane very similar to the first." 

 This inner membrane I regard as the true involucre. 



Venation, Fig. 11. ° 



* These observations have reference exclusively to Eupteris aquilina ; they will per- 

 haps require modifying, since a North American species, which appears to be uniform- 

 ly less rigid than aquilina, must unquestionably be included in the same genus. 



1 1 here quote a previously published description of Pteris aquilina. 



