158 



SYSTEMATIC BOTANY. 



it is naturally divided into two Provinces, founded upon their 

 mode of vegetation. The Acrogens include those tribes which 

 make some approach toward the Pha3nogams, while the Thallo- 

 gens include the lowest tribes of the vegetable kingdom. They 

 are thus distinguished 



ACROGENS 'otxpov the summit or point, THALLOGENS (^JtXXov, green expansion, 



Flowerless Plants having a regular stem Flowerless Plants producing in vegetation 



or axis, which grows by the extension of a thallus an indefinite expansion or mass, 



the apex only, generally with leaves, and with no distinction of stem, leaf, or root, 



composed of cellular tissue and scalariform composed of cellular tissue only (Lichens, 



ducts (Ferns, Mosses, Club-mosses, Horse- Fungi, etc.) 

 tails, etc.) 



517. Classes of the Flowerless Plants. For the sake of 

 analogy and an advantageous comparison with the Pha3nogams, 

 we may also regard these two provinces of the Cryptogams in 

 the light of Classes founded upon their different modes of fruit- 

 bearing. Thus the Acrogens constitute the class 



ANGIOSPOR.E (ayy?io, (f'Tr'opa), or Angiospores : 



Acrogenous plants, producing their spores in sporangia (vessels) which bt.rst 

 when the spores are mature. 



And the Thallogens constitute the class 



GYMNOSPOR^E (yu;xvo, CVopoc), or Gymnospores : 



Thallogcnous plants reproduced by spores, which are produced in parent cells, 

 either forming a part of the vegetating thallus, or growing upon the surface of some 

 definite region of the thallus. 



518. The class AXGIOSPORES is divided into three cohorts (or 

 Alliances according to Lindley) : 



Lycopodales. Acrogens with vascular tissue, spores of two kinds, and spore-cases axil- 

 lary or radical, one many-celled. Plants with well-developed leaves. (Lycopodiacece, 

 Marsileaccae.) 



Filicales. Acrogens with vascular tissue, spores of but one kind, spore-cases borne on 

 the margin, back, or summit of the frond, one-celled, usually girded by an elastic ring. 

 Plants leafy or sheathed. (Equisetaceie, Filices.) 



Muscales. Acrogenous plants mostly cellular, with two kinds of floral organs (antheri- 

 dia and archegonia), and spore-cases (thecae) either hooded or immersed in the substance 

 of the frond. (Mosses, Hepaticse, etc.) 



519. The class GYMXOSPORES also consists of three cohorts: 



Lichenales. Thallogens growing in air, crustaceous, without mycelium, including 

 spores plunged in the thallus as well as in shields. (Lichens.) 



Algales. Thallogens living in water or very damp places, cartilaginous, brightly colored, 

 without mycelium, nourished through their who! 3 surface. (Algse, or Seaweeds.) 



Fungales. Thallogens fructifying in the air, never green, nourished by their own my- 

 celium, which is immersed in, and feeds upon decaying substances. (Fungi.) 



