74 



FILICALES. 



[ACROGENS. 



It IS coated by a hard, cellular, fibrous rind, 

 at the apex, and it is itself composed of 



Alliance W.— FILICALES, — The Filical Alliance. 



Filices, Juss. Gen. 14. (1789) ; Sicartz Synops. Filicim (1806) ; Willd. Sp. PI. vol. v. ; R. Brown 

 Prod. 145; Agardli Aph. 115. U822) ; Kaulfuss Emnn. ; Hooker and Greville Icones Filicum 

 Blume, Ft. Javce ; SchotVs Genera Filicum ; Mohl et Martins Plantce Cryptogamicce Brasilienses. 

 p. 40. (1834) ; Hooker Species Filicum ; Brongniart,Vc(j. Fossile/t, p. 141 ; P?-(\<r;. Tentamen pteridogra 

 phice; J. Smith in Hooker Journ. Bot.; Endl. gen. p. 58; Hooker and Bauer, Genera Filicum , 

 Link, Filicum Species. 



Diagnosis. — Vascular AcrogeTis, with marginal or dorsal one-celled spore-cases, usiially 

 surrounded hy an elastic ring ; and spores of only one hind. 



These are leafy plants, producing a rhizome, which creeps below or upon the sm'face 

 of the earth, or rises into the air hke the trunk of a tree ; tliis tinrnk consists of a woody 

 cylinder, of equal diameter at both ends, growing at the point only, containing a loose 

 cellular substance which often disappears ; ' " 

 which is much thicker next the root than 

 the united bases of leaves. Wood, when 

 present, consists almost exclusively of large 

 scalariform or dotted ducts, imbedded m 

 hard plates of thick-sided elongated tissue, 

 which usually assumes an iuteiTupted sinu 

 ous appearance, but occasionally, according 

 to Brown, forms a complete tube in Dipte- 

 ris, Platyzoma, and Anemia. Leaves coikd 

 up iu vernation, with annular ducts hi the 

 vascular tissue of their petiole, eithti 

 simple or di\ided m various degrees, 

 traversed by simple, dichotomous, oi 

 netted veins of equal thickness, which are 

 composed of elongated cellular tissue, with 

 occasional ducts ; cuticle frequently with 

 stomates. Reproductive organs consist- 

 ing of spore- cases arismg from the vems 

 upon the imder sui-face of the leaves or 

 from their margin, either pedicellate, with 

 the stalk passing romid them m the form 

 of an elastic ring, or sessile and destitute oi 

 such a ring ; either springing from beneath 

 the cuticle, which they then force up m 

 the form of a membrane (or indusium), or 

 from the actual surface of the leaver 

 Spores arranged without order within the 

 spore-cases. Sometimes the leaves aie 

 contracted about the cases, so as to assume 

 the appearance of forming a part of the 



^oMn 



^.jf 



biypbog^anify 



reproductive organs, and sometimes the place of spore-case is supplied by the depau- 

 perated lobes of the leaves. 



The plants called Ferns are the most gigantic of Acrogens, sometunes haAong trunks 

 forty feet high. They approach Flowering classes by Cycadacese, which may be considered 

 to have much affinity with them, on account of the imperfect degree in which the vas- 

 cular system of that" Order is developed, of their pinnate leaves vAth a gyrate vernation, 



Fig. LII.— Tree-Ferns, from Blume. 



