FERNS. 



[ 319 ] 



FERNS. 



org. Verb. i. 223 ; Mitscherlich, Pogg. An- 

 na/. Iv. 224 ; Lekrb. 4. ed. 371 : Cagniard 

 Latour, Pogg. Ann. xli. 193; Schwann, 

 ibid. 184 ; Uie,Eiblioth. Genev. 1839 ; Helm- 

 holtz, Miiller's Archiv, 1843, 453 ; Reess, 

 Alcoholgdhrungs - Pilze, 1870 ; Pasteur, 

 Etudes s. 1. Vmaigre, 1868, *. I Tin, 1872, 

 *. /. iere, 1876 ; V. Tieghem, Ann. Sc. Nat. 

 yiii. 1868; Fremy, Gener. d. Ferments, 1875; 

 Schutzenberger, Ferment. 1875; Gayon, 

 Ann. Sc. Nat. 1875, i. 5 ; Muntz, Ferment, 

 Compt. Rend. 1878 (Jn. Mic. Soc. 1878, 

 23) ; Lister, Qu. Mic. Jn. 1878, xviii. 177 ; 

 Nageli, Theor. d. Gahrung, 1879 ; Sachs, 

 JBot. 254 ; Tyndall, Putrefaction $c. 1881. 

 See also TORTJLA and PENICILLIUM. 



FERNS. This class of Flowerless Plants 

 offers very many points of interest to the 

 microscopist ; and indeed the use of magni- 

 fying-instruments is indispensable in their 

 examination for botanical purposes. The 



Fig. 221. 



Scolopendrium vulgare ; underside of frond. 

 Nat. size. 



Ferns are characterized by the position of 

 their spore-cases or fruits (thecae, sporangia, 

 or capsules), which are collected into what 



to the naked eye look like spots, streaks, 

 or patches of a brown colour (son) at the 

 back or lower surface of the leaves or fronds 

 (fig. 221), or at their margins, these fer- 

 tile leaves either resembling the rest, or 

 being modified in a manner which more or 

 less disguises their nature, as in what are 

 miscalled ' flowering Ferns' (Osmunda (figs. 

 222 & 223), Botrychium, &c.). 



The Ferns possess a stem which is more 

 or less developed in different cases : in our 

 native kinds it is either a slender, horizon- 

 tal, subterraneous rhizome or rootstock, or 

 a thick, short, erect one rising little above 

 the ground ; but in foreign kinds this erect 



Fig. 222. 



Fig. 223. 



Osmunda regalis. 



Fig. 222. Upper part of a frond, l-6th nat. size. 

 Fig. 223. A fertile pinnule bearing thecse without 

 parenchyma. Magnified 10 diams. 



stem attains the forms and dimensions of a 

 tree, growing up into a tall unbranched co- 

 lumnar stem, sometimes more than fifty feet 

 high. The anatomical structure of the 

 stem of the Ferns is peculiar and special, 

 depending on the character and arrange- 

 ment of the fibro- vascular bundles (see 

 TISSUES, VEGETABLE), which afford the 

 best examples of that form of elementary 

 tissue called the SCALARIFORM DUCTS. The 

 creeping rhizomes are often clothed more 

 or less thickly (as are also the leaf- stalks) 

 with brown membranous scales called RA- 

 MENTA ; and these often afford elegant mi- 

 croscopic objects, from the peculiar arrange- 

 ments of the cells. The leaves are gene- 

 rally very greatly developed ; and the green 

 blade is of more or less complex structure 

 in different genera. In the Hymenophylla, 



