FILICINEM. 44 T 



ultimate branches of which the sporangia are developed as if they were metamorphosed 

 lacinige. The ovoid or pear-shaped sporangia are sessile, the apex of each being occu- 

 pied by a cap-like zone of peculiarly-formed cells. The dehiscence is longitudinal. The 

 stem (also in Lygodium) does not branch much, and is but feebly developed, A single 

 fibro-vascular bundle traverses the petiole. The leaves of Lygodium resemble twining 

 stems. 



Family 3. GleieheniaceaB. The sessile sporangia are borne upon the dorsal surface 

 of ordinary leaves. They form sori of usually three or four sporangia, and no indusium 

 is developed. The sporangium has a complete transverse annulus, and longitudinal 

 dehiscence. The stem is a thin, creeping rhizome. The lamina of the leaf is remark- 

 able for its innovation. 



Family 4. HymenophyllaceaB ^. The sporangia have an oblique or transverse 

 complete annulus; and therefore burst with a longitudinal slit; they are formed on 

 a prolongation of the fertile vein (the Columella), projecting beyond the margin of the 

 leaf, which is surrounded by a cup-shaped indusium. The mesophyll of the leaves 

 usually consists of a single layer of cells, and is then necessarily destitute of stomata, 

 which do however occur in Loxsoma on the leaf, which then consists of several layers. 

 The stem is generally creeping and mostly very slender, and furnished with an axial 

 fibro-vascular bundle. True roots are not present in all the species; where they 

 are absent, the stem itself is clothed with root-hairs: a large number of species 

 of Trichomanes are described by Mettenius as rootless, and in these cases branches 

 of the stem assume a deceptive root-like appearance. The development of the axes 

 precedes by a long space that of the leaves ; several internodes have usually completely 

 ended their growth while the leaves belonging to them are still very small ; and these 

 apparently (or actually?) leafless shoots often branch further to a great extent. The 

 formation of the tissue of these families shows also many peculiarities, concerning which 

 reference must be made to Mettenius (Hymenophyllaceae, /. c). The fertile end of the 

 veins of the leaf projecting beyond its margin, the columella, elongates by intercalary 

 growth, and the newly-formed sporangia are, in a corresponding manner, produced in 

 basipetal succession. They are arranged in a spiral line on the columella. The almost 

 sessile sporangia are biconvex, and are attached to the columella by one of their convex 

 surfaces. The annulus projecting in the form of a cushion which separates the two 

 convexities is usually oblique, and divides the circumference into two unequal portions. 

 In Loxsoma the sporangia are pear-shaped and distinctly stalked. Paraphyses occur only 

 in a few species of Hymenophyllum. 



Family 5. CyatheacesB. The sporangia are shortly stalked and have a complete, 

 oblique, eccentric annulus. They are borne upon a strongly-developed placenta 

 forming a closely-packed sorus, which is either naked or invested by an indusium, which 

 may be cup-shaped or completely encloses it. The genera Cibotium, Balantium, Alsophila, 

 Hemitelia, and Cyathea include the so-called Tree-ferns, with a lofty, erect, unbranched 

 stem, often thickly covered with roots, bearing at its apex a rosette of large usually 

 compoundly pinnate leaves. 



Family 6. PolypodiaceaB. The sporangia are borne in great numbers on the under 

 surface of usually unmodified leaves. They have a vertical incomplete ring, and they 

 dehisce transversely. The following subdivisions of this family, which contains the largest 

 number of species of any, may be distinguished : — 



(a) Acrostichex. The sori cover the surface and veins of the under side or of both 

 sides, or are placed upon a thickened placenta which stands on the vein. There is 

 no indusium. {Jcrostichum, Polybotrya.) 



(b) Polypodiedd. The sori are rounded or linear, and terminal or lateral on the veins. 

 They are naked. The leal-stalk is either articulated to the stem {Pclypodium), or is not 

 {Phegopteris.) 



^ [Prantl, Die Hymenophyllaceen, 1875.] 



