r 
395 
Class V. ACROGENS, or FLOWERLESS PLANTS. 
Acotyledones, Juss. Gen. 1. (1789). — Exembryonat^ or Arhizm, Rich. Anal, du Fr, 
(l^'OB). — Cellulares, DC. FI. Fr. 1. 68. (1815); Lindl. Synops. p. S. (1829). — 
AcoTYLEDONEiE and PseudocotyledonejE, A^ardh. Aph. 72. (1821). — Agamaj, 
Cryptogamous or ^Etheogamous Plants of authors; Ad. Brongniart in Diet. 
Class. 5. 155. (1824). — Nemea, Fries. Syst. Orb. Veg. 1. 30. (1825). 
Essential Character. — Substance of the plant usually composed of cellular tissue 
chiefly, either in a spheroidal or elongated state ; spiral vessels or ducts only present in 
the highest orders. Stem either increasing hy an extension of its point, or by a regular or 
irregular developement in all directions from one common point ; not increasing percepti- 
bly in thickness or density when once formed. Cuticle generally destitute of stomates. 
Sexual organs, and consequently flowers absent. Reproduction taking place either by 
spores or sporules, which are enclosed in cases called thecce, or imbedded in the substance 
of the plants ; or else by a mere dissolution of the utricles of cellular tissue ; germination 
occurring at no fixed point, but upon any part of the surface of the spores. 
Such are the characters by which this class of the vegetable kingdom is 
distinguished from the last ; characters of so marked a kind as to render it 
impossible to refer individuals of one to the other. The universal want of 
flowers, and of all kinds of perfect sexual apparatus ; the general absence of 
spiral vessels, the place of which is occasionally supplied by annular or scala- 
riform ducts ; the non-existence of a true trunk (for the stipes of Ferns, 
composed only of the united bases of the leaves or fronds, is scarcely analogous 
to the trunk of Vascular plants) ; and, finally, the near approach in the most 
simple tribes, such as Arthrodiese and Chaodinese, to the nature of infusorial 
animalcules, are all facts, the accuracy of which is undisputed, and which have 
no parallel in flowering plants. With regard to their stem, instead of its 
increasing by the deposition of matter originating in the leaves, it appears to 
be a mere extension of some common vegetating point, which becomes cylin- 
drical and long, when it is capable of being acted upon by the influence of 
light, as in Ferns, Lycopodiacese, &c. ; which expands irregularly and remains 
flat and foliaceous in such orders as Hepaticee and many Algse ; which 
developes in straggling threads in some of the latter ; and which collects these 
threads into masses of reproductive matter in Fungi. It is true that sexual 
apparatus has been described by various authors in many of the tribes of 
Acrogens ; but it is equally certain, that if such a provision for propagatioi 
ever exists, it is in a most imperfect state, and by no means analogous to what 
we call the sexes in flowering plants ; and it is even conjectured that tht 
simplest forms of Lichens, Fungi, and Algae, are produced by a kind of equi- 
vocal generation, from a common form of matter having no inherent special 
tendency to control its mode of developement, but appearing as a Lichen, 
Alga, or Fungus, according to the peculiar conditions of soil and atmosphere 
under which it is called into action. Upon this subject more will be said, in 
speaking of those orders hereafter. 
Flowerless may be said to approach Flowering plants by Ferns, which 
have a certain relation to Cycadacese, by Lycopodiacese, which may be com- 
pared in many respects to Coniferae, and by Equisetacese, which have a great 
external resemblance to Casuarina. 
The subject of Cryptogamic botany is not less obscure than extensive ; 
it is usually among botanists, an object of separate attention, especially in 
the lower tribes ; and I think I shall best consult the interest of readers of 
