FILICINEAE. HOMOSPOROUS FII.ICINEAE. 197 



tineae and Lycopodineae the entire external form is determined by the structure and 

 branching of the stem, and the most important physiological duties are committed to 

 it ; but in the Filicineae the stem is essentially only the bearer of the leaves and 

 roots, and grows very slowly in length, in many species not even forming distinct 

 internodes ; the leaves, on the contrary, are distinguished by vigorous apical growth 

 lasting a long, sometimes an unlimited time. The stem too in the Filicineae shows 

 little tendency to branch ; in entire sections it is always simple, and the formation of 

 new buds is not unfrequently effected by the agency of the leaves, in which the 

 tendency to branch is expressed in every variety of pinnation, dichotomous division 

 and formation of lobes. In the Equisetineae and Lycopodineae the stem usually 

 takes part in the formation of the inflorescence ; this is always in the Equisetineae and 

 generally in the Lycopodineae a terminal sporangiferous spike which puts an end to 

 the longitudinal growth of the branch on which it is formed ; such an arrangement never 

 occurs in the Filicineae ; the work of propagation is assigned to the leaves only, the 

 stem takes no part in it at all. The number of sporangia formed on a leaf of the 

 Filicineae corresponds with its size and is usually very large, whereas the small 

 sporophylls of the Equisetineae bear but few sporangia ; those of the Lycopodineae 

 only one. The mode of formation of the sporangia on the leaves of the Filicineae 

 varies considerably ; in the Ophioglosseae they are sunk in the tissue of the 

 sporophyll; in the Polypodiaceae they are capsules with long stalks. Among the 

 heterosporous forms the Salviniaceae come very near to the Polypodiaceae, 

 Cyatheaceae, and their allies in respect of their ' fructification,' while more complicated 

 processes take place in the Marsiliaceae, where the sporangia are inside capsules of 

 peculiar construction termed spore-fruits or sporocarps, 



A. LEPTOSPORANGIATE FILICINEAE (FERNS) 1 . 

 1. HOMOSPOROUS FILICINEAE. 



The first or sexual generation (pophore, oop/y/e], the prothallium, is a thallus 

 which is rich in chlorophyll and self-supporting ; its development offers many 

 striking points of resemblance to that of the thallus of the simpler Hepaticae, and 



1 H. v. Mohl, Ueber d. Bau d. Stammes d. Baumfarne (Vermischte Schriften, p. 108). Hof- 

 meister, Ueber Entwickl. u. Bau d. Vegetationsorgane d. Fame (Abh. d. kon. Sachs. Ges. d. Wiss. 

 1857, V). Id., Ueber d. Verzweigung der Fame (Jahrb. f. wiss. Bot. Ill, 278). Mettenius, Filices 

 horti bot. Lipsiensis, Leipzig, 1856 ; Id., Ueber d. Hymenophyllaceen (Abh. d. kon. Sachs. Ges. d. 

 Wiss. 1864, VII). Wigand, Bot. Unters., Braunschweig, 1854. Dippel, Ueber d. Baud. Fibrovasal- 

 strange, in dem Ber. deutscher Naturf. u. Aerzte in Giessen, 1865, p. 142. Rees, Entw. d. Poly- 

 podiaceensporangiums (Jahrb. f. wiss. Bot. V. 5, 1869). Strasburger, Befruchtung d. Farnkrauter 

 (Jahrb. f. wiss. Bot. VII, p. 390, 1869). Kny, Ueber Entw. d. Prothalliums u. d. Geschlechtsorgane 

 in d. Sitzungsber. d. Gts. naturf. Freunde in Berlin, .1868 am 21 Januar. u. 17 Nov.; Id., Ueber 

 Bau u. Entw. d. Farnantheridiums (Monatsber. d. kon. Akad. d. Wiss. Berlin, 1869, Mai); Id., 

 Beitr. z. Entwicklungsgesch. d. Farnkrauter (Jahrb. f. wiss. Bot. VII, p. i). Russow, Vergleichende 

 Unters., Petersburg, 1872. Janczewski, Ueber d. Archegonien (Bot. Zeit. 1872, p. 418). Kny, 

 Die Entw. d. Parkeriaceen (Nova Acta Ac. Leop. Car., Bd. 37). Prantl, Unters. z. Morphol. 

 d. Gefasskryptogamen, Heft i u. 2 (Hymenophylleen u. Schizaeaceen). [Rabenhorst, Kryptog. 

 Fl. Die Gefasskryptog. v. Ch. Luerssen, 1885. Goebel, Vergl. Entwgs. d. Pflanzenorg. in 

 Schenk's Handb. d. Bot. III.] Other treatises are given further on. Sadebeck has recently 

 published an exhaustive account of the Vascular Cryptogams in Schenk's Handbuch d. Botanik, I Bd. 



