256 



GENERA INCERTAE SEDIS 



[CH. 



mass, sometimes flattened but not characteristically scaly. It contains a 

 solenostele surrounding a sclerotic core : but transitions are found towards 

 dictyostely. The erect leaves are a foot or more in length, and are simply 

 pinnate, with leathery pinnae traversed by a mid-rib, and on either side a 

 closed reticulum extending to the margin, but without any free vein-endings 

 within the areolae. The petiole is traversed by two vascular straps, but the 

 leaf-trace separates as a single sector from the stele: soon it divides into 

 two by a perforation that dies out before the lowest pinnae are reached. The 

 pinna-traces are of marginal origin. 



The sporophylls resemble the sterile leaves: but each is traversed longi- 

 tudinally by a coenosorus parallel to the margin, giving the appearance of 

 having been imposed upon the reticulum 

 without disarranging it, along a line about 

 half- way between the mid-rib and the margin. 

 There is no indusium (Fig. 751). The sorus 

 consists of sporangia of mixed origin, asso- 

 ciated with numerous glandular hairs, which 

 are often closely related to their stalks. The 

 glandular hairs precede the sporangia in 

 development, and overarch them while young 

 like a forest-canopy (Von Goebel). The spo- 

 rangia are of an ordinary Leptosporangiate 

 type, with annulus interrupted at the stalk, 

 having 16-18 indurated cells. The stalk con- 

 sists of three cell-rows, and the spores are 

 tetrahedral, and appear to be without any 

 saccate perispore: but they bear a peculiar 

 solid equatorial ring (Hannig, Flora, Bd. 103, 

 p. 341). The development of the coenosorus |^' 

 has not yet been traced from the beginning, 

 but its origin can hardly be other than 

 superficial. The sporangia arise from a shallow furrow, with no independent 

 or regular underlying commissure: the coenosorus often follows short lengths 

 of the veins, but it bridges over the gaps between them : thus it is not dependent 

 upon the venation. In fact Taenitis presents a peculiar type of coenosorus: 

 in particular it does not correspond to that of Pteris either in position or 

 in vascular supply, but it seems nearer in its mode of origin to Blechnuvi. 

 Not unfrequently it may be interrupted (Hook. & Grev., hones Fil. PI. LXIII ; 

 Von Goebel, /.c. Taf x. Figs. 68,72): such examples confirm the impression 

 of the coenosorus as being imposed upon a pre-existent reticulum. 



These characters indicate Taenitis as an isolated type. A careful consider- 

 ation of them led Von Goebel to conclude that there are relations between 



Taenitis blechnoides (Willd.) 

 Sw. , venation of part of a fertile leaf-seg- 

 ment, showing an irregular commissure 

 below the soral tract. (After Leonard.) 



