FERNS. 



[ 262 



FIBRINE. 



other cellular bodies of more complex struc- 

 ture, which are the archegonia or ovule-like 

 bodies. The archegone consists of a cellular 



papilla, composed of a few colourless cells, 

 with a canal running down its centre (an 

 intercellular passage) leading to a cell (em- 



Fig. 240. 



Fig. 241. 



Fig. 242. 



Fig. 243. 



Germination of Pteris longifolia. Magn. 100 diams. 



hryo-cell) at the bottom, contained in a cavity 

 { embryo-sac) in the substance of the prothal- 

 lium. It is supposed that the ciliated spiral fi- 

 laments make their way down this canal, like 

 the pollen-tubes through the micropyles of 

 Phanerogamous ovules( Hofmeister states that 

 he has actually seen this), and then the em- 

 bryo-cell becomes developed into an embryo, 

 which soon exhibits rudimentary leaves and 

 rootlets, bursts out from the cavity of the 

 prothallium (which decays away), and grows 

 up into the ordinary leaf-bearing stem of the 

 Ferns (fig. 244). The pro- 

 thallia bear a variable number 

 of archegones, but not nearly 

 so many as of antherids, and 

 they exhibit, in most fully- 

 developedspecimens,anumber 

 of effete organs of both kinds, 

 which are readily distinguished 

 by the deep brown colour as- 

 sumed by the membranes 

 lining their cavities. 



The Ferns likewise produce gemmce on the 

 leaves of full-grown plants, and even the 

 prothallia are capable of vegetative multipli- 

 cation ; for if their archegones are all abor- 

 tive, they go on vegetating for a long time, 

 and produce new prothallia by some of their 

 marginal cells budding out and repeating 

 the original mode of growth of the spore 

 itself. These innovations usually bear an- 

 therids alone, and not archegones. 



The Ferns are divided into four families 

 by microscopic characters. 



1. PoLYPODiACE^. The sporanges on 

 the lower surface of the leaves, in groups 

 of very varied form, but never blended to- 



Pteris, seedling. 



gether. The annulus always exists, is vari- 

 able, and serves to distinguish the tribes. 



2. Marattiace^. Sporanges on the 

 lower surface of the leaves ; usually blended 

 together, sometimes only very closely ap- 

 proximated ; without an annulus. 



3. Ophioglosse^. Sporanges on the 

 lower surface of the leaf (reduced to mere 

 ribs); never blended together; without an 

 annulus. 



4. Hymenophylle^. Sporanges at- 

 tached to a common stalk prolonged from 

 the end of a vein of the leaf, and contained 

 in a kind of cup formed by a lobe of the leaf 

 above and an indusial lobe of similar charac- 

 ter prolonged from the lower surface of the 

 leaf. Sporanges with an obliquely trans- 

 verse annulus. 



BiBL. Hooker, Genera Filicum ; Presl, 

 Tent amen PteridographicB, Prag, 1836; 

 F?iyen,BotaniqueCryptogamique, Paris, 1850; 

 Bischoff*, Kryptogamische Gew«c^se,Nuremb. 

 1828 ; Mohl (Structure), in Martins' s Plant. 

 Kryptog. Brazil ; Moore, Handbook of Bri- 

 tish Ferns ; Newman, British Ferns. For 

 minute particulars of the reproduction, see 

 Henfrey, On the Development of Ferns from 

 their Spores, Linnean Transactions, vol. xxi. 

 p. 117- 1853, On the Reproduction of Crypto- 

 gamia, Annals of Nat. History, 1852, and 

 the papers of Suminski, Hofmeister, Mette- 

 nius, De Mercklin, Thuret, and others there 

 quoted; Hofmeister, Ann. Nat. Hist. xiv. 

 p. 272. 



FIBRINE. — Fibrine is soluble in, or ren- 

 dered so transparent by acetic acid, as to be 

 invisible. Its chemical relation to the other 

 proteine-compounds has not been satisfacto- 



