ACROGENS. 115 



ENDOGENS, 



1. Growing by internal accretions (197). 



2. Leaves parallel-veined (229) and decaying without falling off. 



3. Seeds with one cotyledon (126) or monocotyledono-us. 



349. Classes. The groups above mentioned, comprising the 

 whole vegetable kingdom, are again subdivided into six classes. 

 The first two are formed from the subdivision Exogens, and are 

 founded upon the presence or absence of the pericarp ; namely, 



Class I. ANGIOSPERMS, (as the oak, rose,) 



1. Ovules produced within an ovary, and 



2. Fertilized by the action of the pollen through the stigma, 



3. Becoming seeds enclosed in a pericarp. 



4. Embryo with two opposite cotyledons. 

 Class II. GYMNOSPERMS, (as the pine, yew,) 



1. Ovules produced naked beneath a scale-like carpel. 



2. Fertilized by the direct action of the pollen without the stigma, 



3. Becoming truly naked seeds, that is, destitute of a pericarp. 



4. Embryo mostly with several whorled cotyledons. 



350. The next two classes are formed from the subdivision 

 Endogens, and are founded upon the presence and absence of 

 glumes or husks ; namely, 



Class III. AGLU3IACE.E Or AGLUMACEOTJS ENDOGENS, 



Plants of the endogenous structure with flowers constructed on the 

 usual plan; perianth verticillate, of one or more whorls of petaloid 

 organs, or wanting. Ex. lily, orchis, rush. 

 Class IV. GLUMACE^E or GLTJMACEOUS ENDOGENS, 



Plants of the endogenous structure, the flowers invested in an imbri- 

 cated perianth of glumes instead of a calyx ; as the grasses, grains, 



351. The Cryptogamia are separated into two great classes, 

 called Acrogens and Thallogens ; the former including those 

 tribes which make some approximation towards the Phaenoga- 

 mia, and the latter including the lowest tribes of the vegetable 

 kingdom. As their names indicate, they are distinguished from 

 each other by their manner of growth ; thus, 



Class V. ACROGENS (growing from oeo?, the summit or point) have a regular 

 stem, or axis, which grows by the extension of the point, or apex only, 

 without increasing at all in diameter, generally furnished with leaves, 

 and composed of cellular tissue and ducts. Ex. ferns, mosses, club- 

 mosses, and the Equisetacese. 



