26 EASY LESSONS IN VEGETABLE BIOLOGY. 



application. The terms of natuinl science are no more 

 difficult than those of geography or of history. 



5. The types, or general plans of structure, found 

 in vegetable Biology may be described briefly as 

 follows : 



1.) PKOTOPHYTES, (Greek protos, first, and phuton, a 

 plant.) The first or simplest forms of plants vege- 

 tables composed of a single cell, or mass of bioplasm. 



2.) THALLOGENS, (Gr. thallus, a frond, or vegetable 

 expansion, and ginomai, to produce or grow.) Plants 

 composed of a tissue of cells, or bioplasts, but with no 

 clear distinction of stem, root, and leaves. 



3.) ACROGENS, (Gr. aJcra, summit, and ginomai, to 

 grow.) Plants which grew at the summit only, and 

 not in diameter. 



4.) ENDOGENS, (Gr. endon, within, and ginomai, to 



grow.) Plants whose vessels and woody fibers first 



t 



grow within the stem. The seed has but a single 

 lobe, or cotyledon. 



5.) EXOGENS, (Gr. exo, outward, and ginomai, to 

 grow.) Plants whose woody fibers grow in outer lay- 

 ers. The seed has two lobes, or cotyledons. 



Under these five types or plans of structure all the 

 multitudes of plants which clothe the earth or dwell 

 in the sea can be arranged. 



