34 CLASSIFICATION. 



jfotrs and ENDOGENOUS plants, more briefly named EXOGENS and 



rEJts. The difference between tbe two 'not only pervades 

 their whole port and aspect, but is manifest from the earliest - 



.mbryo of Exogens, as already shown, is provided with a pair 

 of cotyledons, that of Endogens with only one ; whence the for- 

 mer are also termed DICOTYLEDONOUS, and the latter MONOCOTY- 

 plants : names introduced by Jussieu, the father of this 

 branch of botany. We employ sometimes the one and sometimes 

 Aher of the two sorts of names for these two great classes. 



i. In contemplating the Exogenous or Dicotyledonous class, 

 we find that two sets of the plants it comprises are specially dis- 

 tinguished by a great simplicity in their organs of fructification, 

 approximating not indistinctly to that still greater simplicity which 

 characterizes the highest Cryptogamous plants (108). These are 

 the Coniferous trees, such as Pines, Firs, &c., and that small and 

 singular tribe of Endogenous port but essentially Exogenous struc- 

 ture, which comprises the Cycas and Zamia (Fig. 403) : in these 



. not only are the sterile or staminate flowers reduced to the 

 last degree of simplicity, but the fertile consist of naked ovules 



y, borne on the margins or surface of a sort of open leaf, in- 

 stead of being inclosed in an ovary (560, 111). They are there- 

 fore named GYMNOSPERMOUS (that is, naked-seeded) plants ; and 

 form a subordinate group, or subclass, of Exogens. When it is 

 needful to contradistinguish the great mass of Exogens from which 



are thus separated, we call them ANGIOSPERMOUS Exogenous 

 plants ; a name denoting that their seeds are inclosed in a pericarp. 



jch reduction occurs in the Endogenous class. 

 091. We must next consider the systematic division of the Flow- 



, or Cryptogamous series. This is most readily accomplished 

 by conceiving them to present a series of reductions or degrada- 

 tions of a higher type. In their general mode of growth, and in 

 their anatomical structure, the higher Flowerless plants, such as 

 Equiseturns, Club-Mosses, and Ferns, do not essentially differ from 

 Flowering plants. All the various kinds of elementary tissue, 

 proper woody fibre, vessels, &c., enter into their composition (108, 

 10!);. If we had chosen to take anatomical structure as the basis 

 of our primary division of the whole vegetable kingdom, we might 

 have divided the whole into Vascular and Cellular plants (107), as 

 was done by I)e Candolle ; the former comprising the whole series 

 from Ferns upward, the latter embracing the Mosses and all below 



