340 



VASCULAR CRYPTOGAMS. 



CLASS VL 



FE RNS^. 



The Sexual Generation or Prothallium is a thalloid structure containing chlo- 

 rophyll and obtaining its nourishment independently ; its development presents 

 striking resemblances to that of the simpler Hepaticai, and to a certain extent 

 even to the formation of the pro-embryo of some IMosses. It produces simple 

 tubular unarticulated root-hairs, and finally antheridia and archegonia. Its develop- 

 ment and the duration of its life may embrace a considerable space of time, espe- 

 cially when the archegonia are not fertilised. 



When the spores germinate, which usually does not take place till a con- 

 siderable time after dissemination (but in Osmunda after only a few days) the cuti- 

 cularised exospore, generally provided with ridges, bosses, spines, or granulations, 

 splits along its edges ; the endospore, which now protrudes and is not unfrequently 

 already divided by septa, produces the prothallium, either immediately, as in Os- 

 munda, or after the preliminary formation of a filamentous pro-embryo, which pre- 

 sents in Hymenophyllaceje certain resemblances to that of the Andreasaceae and 

 of Tetraphis among IMosses. The development of the prothallium has been more 

 exactly investigated only in the Hymenophyllacese, the Polypodiaceae, and also 

 in Osmunda and Aneimia ; and the considerable diff'erences which have thus been 

 established necessitate separate descriptions. 



In the Hymenophyllacese the contents of the spore are divided, even before 

 germination, into three cells meeting in the centre ; in some species of Trichomanes 

 small cells are cut off at three points of the circumference, while a large central 



^ H. von Mohl, Ueber den Bau des Stammes der Baumfarne (Verm. Schriften, p. loS). — Hof- 

 meister, Ueber Entwickelung imd Bau der Vegetationsorgane der Fame (Abhandlungen der konigl. 

 Siichs. Gesells. der Wissen. 1857, vol. V). — Ditto, Ueber die Verzweigung der Fame (Jahrb. fiir 

 wissen. Bot. vol.111, p. 278). — Mettenius, Filices Hort. Bot. Lipsiensis (Leipzig 1856). — Ditto, Ueber 

 die Hymenophyllaceen (Abhandlungen der konigl. Sachs. Ges. der Wissen. 1864, vol. Vll). — Wigand, 

 Botanische Untersuchungen (Braunschweig 1854). — [On the Germination, Development, and Fruc- 

 tification of the Higher Cryptogamia, &c. Ray Society, 1862, pp. 128-266.] — Dippel, Ueber den 

 Bau der Fibrovasalstrange in the Berichte deutscher Naturforscher u. Aerzte in Giessen, 1865, 

 p. 142. — Rees, Entwickelung des Polypodiaceensporangiums (Jahrb. flir wissen. Bot. 1866, vol. V. 

 p. 5). — Strasburger, Befruchtung der Farnkrauter (Jahrb. fiir wissen. Bot. 1869, vol. VII, p. 390). 

 — Kny, Ueber Entwickelung des Prothalliums und der Geschlechtsorgane, in the Sitzungsberichte 

 der Gesellschaft naturforschender Freunde in Berlin, Jan. 21 and Nov. 17, 1S68. — Kny, Ueber Bau 

 und Entwickelung des Farnantheridiums (Monatsberichte der kais. Akad. der Wissen. Berlin, 

 May 1869). — Kny, Beitrage zur Entwickelungsgeschichte der Farnkriiuter (Jahrb. fiir wissen. Bot. 

 vol. VII. p. I). 



