CLASS II.— ACEOGENS. Lindley. 



AcROGEN^, Brongn. — Acrobeya, Mohl., Endl. — PsbudocotyledonEjE, 

 Ag. — Hetbeoneme^, DiPLoaENEA, Crtptandra, Fr* 



Mostly herbaceous, provided with distinct often stomatiferous 

 appendages, and frequently containing vascular as well as 

 celkilar tissue. Spores producing a prothallus or developed 

 at once into a perfect plant. Spermatozoids spiral. The 

 characters may be given in terms of the distinctive names 

 as follows : 



1. Vascularia, KeteronemecB, Diplogenece. 



2. Acrogence, Acrobrya. 



3. PseudocotyledonecB, Cryptandra. 



462. The second great class into which Cryptogams are 

 divided, with the exception of Characece and a few obscure 

 HepaticcB, is at once distinguished by the presence of foliaceous 

 appendages bearing some resemblance to those of Phcenogams. 

 In many instances stomates are present, and the functions are, 

 to a greater or less extent, the same. The stem itself in many 

 cases has distinct vascular tissue. Even in those plants, as 

 JungermannicB, where vascular tissue is very rare, we have 

 distinct unreliable spiral vessels in the elaters. In mosses again, 

 which have no elaters, genera exist, as Sphagnum, in which 

 the leaf-cells contain a well-developed spiral. Such tissue is 

 often scalariform ; but in Isoetes and Equisetum it is distinctly 

 annular, with transitions to short spirals ; while in Selaginella 



* With the exception of the names used by Fries and Brongniart, 

 the above terms are not absolute equivalents of Acrogens, as under- 

 stood in the present volume, Characece being, for the most part, classed 

 with Thallogens. 



