74 



FILICALES. 



jACROGENS. 



ce 



Alliance W.-FILICALES.— The Filical Alliance. 



wtten. r,m G,«n 14 (1789) ; SicoWs SiMop». KKcmw (1806) ; IF«Zd. £p. P/. yol. v. ; *. Brown 

 ,W 145 %ardhAph. 115. ,1822) ; fa«4/im &««*.; Hooker and Greville Icones FUuum : 

 Mume Fl.Jaiue; Scl'.trs Gn„-ra Filicum ; itfoW rt Martins Plant* Cryptogams Branhenses, 

 D40 (W84) H«* r%fr; *V7icm>. ; Brongniort, Teg. Fosstiee, p. 141; fW. Tentamenpteridogra- 

 pAte; Eflmltt (n //,lr /own*, fiofc; BkW. pen. p. 58; HooAer and Aiuer, Genera FUwum t 

 Link, Filicum Sixties. 



Diagnosis.— Faseufar Acrogens, with marginal or dorsal one-celled spore-cases, usually 

 surrounded by an elastic ring ; and spores of only one kind. 



These are leafv plants, producing a rhizome, which creeps below or upon the surface 

 of the earth, or rises into the air like the trunk of a tree ; this trunk consists of a woody 



vlind.r of equal diameter at both ends, growing at the point only, containing a loose 



ellular substance which often disappears ; it is coated by a hard, cellular, fibrous rind, 

 which is much thicker next the root than at the apex, and it is itself composed of 

 the united bases of leaves. Wood, when 

 present, consists almost exclusively of large 

 sealarifonn or dotted ducts, imbedded in 

 hard plates of thick-sided elongated tissue, 

 which usually assumes an interrupted sinu- 

 ous appearance, but occasionally, according 

 to Brown, forms a complete tube in Dipte- 

 ris,Platyzoma,and Anemia. Leaves coiled 

 up in vernation, with annular ducts in the 

 vascular tissue of their petiole, either 

 simple or divided in various degrees, 



traversed by simple, dichotomous, or 



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 arising from the veins 



upon the under surface of the leaves or 



from their margin, either pedicellate, with 



the stalk passing round them in the form 



of an elastic ring, or sessile and destitute of 



such a ring ; either springing from beneath 



the cuticle, which they then force up in 



the form of a membrane (or indusium), or 



from the actual surface of the leaves. 



Spores arranged without order within the 



spore-cases. Sometimes the leaves are 



contracted about the eases, so as to assume 



the appearance of forming a part of the 





' 



;fAC>.y 



**rfW -._- 





Fig. LII. 



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

 ■<'d lobes of the leaves. 

 The plants called Ferns are the most gigantic of Acrogens, sometimes having trunks 

 forty feet high. They approach Flowering classes by Cycadacete, 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 with a gyrate vernation, 



Fig. LII.— Tree-Fems, from Blume. 



