420 SYSTEMATIC BOTANY. 



Tribe 6. SCHIZ^EKJE. Spar an ye* 

 dorsal; the annulus in the form of 

 a cap on the summit ; dehiscencc 

 vertical. 



Schizaea, Smith. 



Lygodium, Swartz. 



Tribe 7. OSMUNDE^E. Sporanycs 

 stalked, dorsal, or arranged on pinnce 

 assuming a spiked or paniculate aspect 



from the absence of parenchyma be- 

 tween the veins ; annulus incomplete, 

 dorsal ; dehiscence across the vertex. 



Osmunda, L. 



Todea, Willd. 



Tribe 8. MARATTTEJE. Sporanyes 

 free, closely packed in two roios or in 

 a circle, or soldered together so as to 

 resemble a many-celled capsule, each 

 cell opening by a pore; annulus none. 



Angiopteris, Hoffm. 



Marattia, Sm. 



Danaea, Sm. 



Tribe 9. OPHIOGLOSSE^E. Leaves 

 not circinate ; sporanyes 2-valvfd, on 

 the sides of a sjrike or scape, wliit'li is 

 simple or branched ; annulus none. 



Ophioglossum, L. 



Botrychium, Swarlz. 



Structure and Life-history. The Filices or Ferns exhibit a far greater 

 variety of conditions than the Horsetails. Their most remarkable 

 character is the great development of the leaves, the stem being repre- 

 sented in most cases by rhizomes, although in some of the exotic forms it 

 becomes a real trunk, rising above the ground in a manner analogous to 

 the trunks of Palms (fig. 34, p. 38). 



The rhizomes of the herbaceous kinds are subterranean, and grow 

 either horizontally or vertically. In the former the internodes are either 

 developed or undeveloped ; when they are developed, the leaves arise 

 singly from the ground, as in the common Brake-fern (Pteris) and Poly- 

 podium vulyare (fig. 405, ) ; when the internodes are undeveloped, the 

 leaves are tufted, which is always the case when the rhizome is erect, as 

 in Athyrium Filix-fcemina ; and the arborescent kinds likewise exhibit 

 the tufted growth of the leaves from a terminal bud, with little develop- 

 ment of the internodes. The rhizomatous stems frequently branch, in 

 which case the stem bifurcates, as in the Lycopodiaceae. 



The leaves of the Ferns resemble those of the Phanerogamia in their es- 

 sential structure ; they are very remarkable for their multifold compound 

 forms. The venation or ribbing exhibits a peculiarity, the ramification 

 of the veins in the laminae being on a bifurcated plan (fig. 495, 6, d), and 

 the subdivisions retaining an equal size. The leaves are also characterized 

 by the circinate vernation (p. 74) which is almost universal in the Order, 

 the only exception being found in the Ophioalossece. 



The fructification or sporiferous apparatus of the Ferns is produced upon 

 the leaves ; and it presents a great variety of modifications, which serve to 

 characterize the principal subdivisions of the Order. The spores are formed 

 in spore-cases or sporanges, little membranous sacs attached by a pedicle 

 to the lower surface of the leaf (fig. 495, b, c, i, &c.) or to a kind of 

 skeleton of the leaf in which the parenchyma is suppressed (o). These 

 spore-cases differ in some essential particulars of structure, in the mode of 

 attachment, and in their relations to each other. 



In most of the Filices the spore-cases possess an annulus or ring 

 (fig. 495, i\ an incomplete ring of thickened cells running round the 

 sac, and assisting, by its contraction when dry, to rupture the sac and set 

 free the spores. In the Polypodies and other tribes it is vertical (fig. 

 495, i) ; in the HymenophyllecK the ring is oblique and unconnected with 



