370 THE PRINCIPLES OF 



Class I. Exogenous or Dicotyledonous Plants ; those 

 with endogenous stems, netted-veined leaves, and dicotyledonous (or 

 rarely polyootyledonous) embryo ; 



Class IL Endogenous or Monocotyledonous Plants ; 

 those with endogenous stems, mostly parallel-veined leaves, and 

 monocotyledonous embryo. 



725. Without entering here into a particular explanation of the 

 diversities of structure which Cryptogamous plants present, suffice 

 it to say that they exhibit three grades of simplification as to their 

 vegetation, which appear to correspond with three different modes 

 of fertilization. Plants of the highest grades of the Cryptogamous 

 series have Avood and ducts in their composition (i. e. they are vascu- 

 lar plants, 111), and display the ordinary type of vegetation, viz. 

 with an axis or stem, bearing distinct foliage. But this stem in 

 structure is neither endogenous nor exogenous, and grows from the 

 apex only, having no primary root ; Avhence these vascular Flower- 

 less plants have been called Acrogens, or Acrogenous plants. 

 Of this kind are Ferns, Lycopodiacete, Equisetacese or Horsetails, 

 &c. These plants, it appears, produce tlieir organs analogous to 

 flowers, and have their fecundation effected, once for all, upon the 

 infantile or gei'minating jilantlet, and the result is the oi'igination of 

 a bud, Avliich develops into the adult plant ; and that bears the fruit, 

 in the form of spoi'e-cases and spores (663). Here then are the 

 characters of 



Class 111. Acrogenous Plants ; Cryptogamous plants, with 

 a distinct axis and mostly with foliage, having wood and ducts in 

 their composition : fertilization occurring upon a transient germinat- 

 ing plantlet, and giving rise to the adult plant. 



726. The other Cryptogamous plants, being composed of paren- 

 chyma only, (or with slight exceptions,) are called Cellular plants 

 (111). Among them the Mosses and Liverworts present for the 

 most part the ordinary plan of vegetation ; their organs analogous 

 to flowers appear in the adult plant ; and the fertilization of the 

 pistillidium gives origin to a sporangium in which a multitude of 

 spores, capable of germination, are developed. These compose 



Class IV. Anophytes : cellular Cryptogamous plants, with 

 distinct stem and fohage, or sometimes these parts confluent into a 



be. The trunks or rootstocks of Water-Lilies appear to be endogenous ; but 

 those who have investigated them minutely, declare that they are not really so. 



