46 PTEROID FERNS [CH. 



Paesia 

 Paesia has always been associated by systematists with Pteridiuvi: in 

 fact the latter has been included in the former genus by Hooker (^Syn. Fit. 

 p. 162). It includes seven species, mostly of smaller size than the Bracken. 

 Like it they have a creeping bifurcating rhizome, bearing ample pinnately 

 cut leaves, with open venation. The dermal appendages are again hairs, not 

 scales. Christ notes as diagnostic the undivided and channelled leaf-trace, 

 with horse-shoe transverse section in the petiole {Farnkr. p. 164). This arises 

 from a typical solenostele(Gwynne-Vaughan,^/z«. Bot. XVII, p. 691). The sori 

 are essentially of the same type as those of the Bracken, but more markedly 

 curved downwards, the upper indusium appearing like a marginal flap. The 

 coenosori do not extend far without interruptions. The development of the 

 sorus has been traced in P. viscosa and scaberida (Studies VII, Ann. of Bot. 

 XXXII, p. 24). It accords with that in Pteridiuni in being basipetal, typically 

 bi-indusiate, and in having a vascular commissure. But the lower indusium, 

 which is closely appressed to the lower surface of the pinnule, is never more 

 than one layer of cells in thickness, and it may frequently be absent alto- 

 gether (Fig. 611). These features accord with the view that Paesia includes 

 Ferns closely related to Pteridmm, but of smaller size and simpler construc- 

 tion of the vascular system : while the sorus is of the same type, but more 

 closely protected, with indications of the obliteration of the lower indusium 

 that find their explanation in its close apposition to the lower leaf-surface. 



LONCHITIS L. 



The third genus included by Prantl in his Lonchitidinae is LoncJutis 

 itself. Its eight species are large upright plants with compound leaves of 

 soft texture, and with pubescent surfaces. The chief distinctive features are 

 the position of the sori mostly at the sinuses of the pinnatifid leaf-segments, 

 and the absence of the inner indusium which has already been seen to be 

 inconstant in Paesia. Observations have been made on L. aiirita L. (incl. 

 L. Lindeniana Hk.), and on L. hirsnta L., a Fern of which Hooker remarks 

 (^Syn. Fil. p. 160) that: "Though in technical character a Pteris, this is far 

 more like the two species of Lonchitis in habit." The two species above 

 named are both now included in Lonchitis\ but they differ in certain details, 

 and it will be seen that they supply further intermediate states between 

 the bi-indusiate Pteroids and the true Pteris with only a single indusium. 



Both species contain in the massive stock a large solenostele, about an 

 inch in diameter. Its origin was traced in L. hirsnta by the late Prof Gwynne- 

 Vaughan, from protostely, through a Lindsaya-std.tQ to solenostely, and 

 occasional perforations may occur in this species (G.-V. MS. notes). In both 

 species the leaf-trace is given off as two distinct straps, separate from one 



