VASCULAR CRYPTOGAMS 21 



Vascular Cryptogams is so convenient, that we have decided to adhere 

 to it, without dogmatising as to its permanent retention. In the 

 boundaries of the families, again, there is equal room for diversity of 

 opinion. Whether to retain the Psiloteae under Lycopodiaceae, and 

 the Isoeteae under Selaginellaceae, and whether to regard the trueFilices, 

 the Marattiaceae, and the Ophioglossaceae as constituting one, two, or 

 three classes, are points on which there is much to be said in favour of 

 classifications different from that which we have decided to adopt. 



LITERATURE. 



Thuret (Zoospores and Antherids) Ann. Sc. Nat., vol. xiv., 1850, p. 214; and 

 vol. xvi., p. 5. 



Hofmeister Germination, Development, and Fructification of the Higher Crypto- 

 gams, Ray Soc., 1862. 



Schacht Die Spermatozoiden, Braunschweig, 1864. 



Dippel (Fibrovasc. Bundles) Ber. Deutsch. Naturf. u. Aerzte, 1865. 



Nageli u. Leitgeb (Root) Nageli's Beitr. z. wiss. Bot., 1867. 



Kny (Prothallium) Sitzber. Ges. Naturf. Freunde, Berlin, 1868. 



Millardet (Prothallium) 1869. 



Russow Vergleich. Unters. , Petersburg, 1872. 



Janczewski - (Archegone) Bot. Zeit., 1872,- p. 418. 



Goebel- (Sporangia) Bot. Zeit., 1880 and 1881. 



Sadebeck Die Gefasskryptogamen, 1880. 



Prantl -Morphologic der Gefasskrypt. , 1881. 



Van Tieghem- Bull. Soc. Bot. France, 1883, p. 169. 



Potonie (Vase. Bundles) Jahrb. Bot. Gart. Berlin, 1883. 



Leitgeb - (Spores) Ber. Deutsch. Bot. Gesell., 1883, p. 246. 



Celakovsky Pringsheim's Jahrb. f. wiss. Bot., xiv., 1884, p. 291. 



Bower (Leaf) Proc. Roy. Soc., xxxvii., 1884, p. 61. 



Rabenhorst Crypt. Flora Deutschland, Vase. Crypt., by Luerssen, 1884-88. 



De Bary Comparative Anatomy of Phanerogams and Ferns, 1884. 



Klein (Dehiscence of Sporange) Bull. Soc. Bot. France, 1884, p. 292. 



Leclerc du Sablon (Spores) Ann. Sc. Nat., vol. ii., 1885, p. 5. 



Campbell (Antherozoids) Ber. Deutsch. Bot. Gesell., 1887, p. I2O. 



Baker -Handbook to Fern Allies, 1887. 



HETEROSPOROUS VASCULAR CRYPTOGAMS. 

 Class I. Rhizocarpeae. 



The Rhizocarpeae or Hydropterideas constitute a class composed of 

 only a small number of genera, none of which includes more than a few 

 species. They grow submerged in or floating on water, and derive their 

 name from the circumstance that the non-sexual organs of propagation 

 are produced in the radicular region, or near the base of the leaves. 



