CLASS III— ACOTYLEDONS. 



I. FILICES, i. 



Acotyledonous PLANTS, very generally perennial and terrestrial, stemless, caulescent, 

 or arborescent. Fronds springing from the upper surface of the creeping rhizomes, or 

 forming regular crowns which terminate erect stems ; hlade leafy, crosier-shaped in ver- 

 nation, stomatiferous, simple, pinnatifid or pinnatisect. 



Ebpkodxjctive oegans composed of capsules (sporangia.) collected into groups 

 (sori), situated on the nerves, at the bade or margin of the frond. SoKi usually covered 

 with a pellicle (indusitim or involucre). Spoeangia opening lengthwise, or girt by an 

 elastic ring which unrolling tears them irregularly. Spokes nv/merous, at first collected 

 in fours in the cells (motlier-cells), filling the sporangium, then freed by the decay of these 

 cells, and developing on the damp soil a cellular escpansion (prothallus), on the lower 

 surf ace of which are developed : — 1. Cellular bodies (antheridia) containing flattened 

 threads, coiled in a helim, furnished with cilia, and moving actively (antherozoids) ; — 

 2. Cellular sacs, open at one end (archegonia), into which the antherozoids enter to 

 fertilize a contained vesicle which is destined to reproduce the plant. 



Perennial, very rarely annual {Gymnogramme leptophylla), terrestrial, or very 

 rarely aquatic (Ceratopteris). Sa?EM sometimes forming a rhizome, which is tuberous 

 and fleshy (Angiopteris), or creeping on soil or rocks or trees, sometimes vertical and 

 arborescent, or rarely twining {Lygodium), or sub-sarmentose and dichotomous 

 (Gleichenia). It is composed of fibro-vascular bundles, disposed in a more or less 

 regular circle around a copious cellular tissue ; each bundle presents at its circum- 

 ference a black zone formed of woody fibres (prosenchyma), and a white centre 

 formed of annular and rayed vessels. The central cellular tissue of the stem com- 

 municates, through spaces between the vascular bundles, with an outer zone of 

 similar tissue. The whole is surrounded by a bark formed of the persistent bases of 

 the branches. 



Foliiferous branches (fronds), springing sometimes from the upper surface of 

 the rhizome, at greater or less distances, and becoming partially or wholly disjointed 

 as the stem lengthens, and new fronds are developed, sometimes crowded and covering 

 the rhizome [then called caudex], the tip of which turns up and emits a crown of 

 fresh fronds [Struthiopteris germaniea, &c.). This arrangement forms the passage 

 to Tree-ferns, in which the stem [caudex) rises vertically, in some species attaining a 

 height of 50 to 65 feet. This stem [often called trunk] grows not only in diameter, 

 but in length, as is shown by the scars of the fronds being at first close together, 

 and afterwards sundered, the spaces between them increasing. Ferns, whether 

 creeping or erect, give off numerous roots, which in the arborescent species extend 



