THE NATURAL SYSTEM OF CLASSIFICATION. 3G9 



Series I. PwuenogAmous (or Phanerogamous) or Flowku- 

 ixg Plants (114, 117), which produce flowers and seeds, the latter 

 containing a ready-formed embryo. 



Series II. Cryptooamous or Floaverless Plants (113, 

 117, 651), whose organs of reproduction are not flowers, but some 

 more or less analogous apparatus, and which are propagated by 

 spores or specialized cells. 



724. "We have next to consider how these two series may be 

 themselves divided, in view of the most general and important points 

 of difference which the plants they comprise exhibit. Whenever 

 Phamogamous plants rise to arborescent forms, a difference in port 

 and aspect at once arrests attention; that which distinguishes our 

 common trees and shrubs from Palms and the like (Fig. 184). On 

 examination, this is found to accompany a well-marked important 

 difference in the structure of the stem or wood, and in its mode of 

 growth. The former present the exogenous, the latter the endoge- 

 nous structure or growth (200 - 203, 207, &c). This difference is 

 ecmally discernible, if not so striking, in the annual or herbaceous 

 stems of these two sorts of Phamogamous plants. A difference is 

 aho apparent in their foliage; the foimer generally luue reticulat- 

 ed, or netted-veined, the latter parallel-veined leaves (27G). The 

 leaves of the former usually fall off by an articulation ; those of the 

 latter decay on the stem (309, 310). The Phamogamous series, 

 therefore, divides into two great classes, namely, into EXOGENOUS 

 and Endogenous plants, more briefly named Exogeks and Endo- 

 gens. The difference between the two not only pervades their 

 whole port and aspect, but is manifest from the earliest stage, in the 

 plan of the embryo. The embryo of Exogens, as already shown, is 

 provided with a pair of cotyledons (or sometimes with more than 

 one pair) ; that of Endogens, with only one ; whence the former are 

 also termed Dicotyledonous, and the latter Monocotyledo- 

 nous plants (128, 641-G43) : names introduced by Jussieu, the 

 father of this branch of botany.* Taking these divisions for classes, 

 we have 



* There is, perhaps, no real and complete exception to the coincidence of an 

 exogenous stem with a dicotyledonous (or polycotyledonous) embryo, and of an 

 endogenous stem with a monocotyledonous embryo. Nyctaginaceous plants 

 and some others have a few vascular bundles scattered through their pith, but 

 the rest of the wood is regularly exogenous. The stalk of Podophyllum imi- 

 tates an Endogen, but the subterranean rootstock is truly exogenous, as it should 



