522 MANUAL OF NATURAL HISTORY. 



FLOWEKLESS-PLANTS. 



Flowerless-plants, corresponding with the Crypto- 

 gamia of Linnseus, comprehend all the remaining 

 forms of vegetable life, and are extremely numerous 

 in individuals, and even in species, of which latter, 

 above twelve thousand have been described, included 

 in about twelve hundred genera. They are sepa- 

 rated into two great classes, in one of which an ap- 

 proach is made in general configuration, in struc- 

 ture, and even in the mode of their fructification to 

 the higher forms of vegetation, while the other de- 

 scends to mere aggregations of vital cells. Their 

 principal characteristics consist in the absence of true 

 flowers, and of distinct sexual organs, such as are 

 found in the more highly developed classes, repro- 

 duction being effected by means of acotyledonous, 

 reproductive bodies named spores, which are formed 

 either in their interior, or on their surface, by the 

 union of (at least in acrogens) two differently en- 

 dowed cells. In size they vary from the lofty tree- 

 Fern to the minute Lichen or microscopic fungus. 

 In many leaves are quite wanting, and where a stem 

 exists, it appears to be composed, unlike that of 

 Endogens or Exogens, of a mere junction of the 

 bases of leaves, the growth being Acrogenous, or on 

 the summit. 



In fossil- or Geo-phytology, Cryptogamic plants 

 occupy an important position, as they appear to have 

 been among the earliest forms of vegetables, their 

 remains being very numerous in palaeozoic strata, 



