THE CLASSIFICATION OF PLANTS 233 
Crass I 
GYMNOSPERMS or seed-plants with naked ova- 
ries, such as pines, spruces, cedars, and many 
other evergreen trees. 
Division II ions 
( Susciass I 
PHANEROGAMS OR 
Crass IIL MoNOCOTYLEDONOUS 
SEED-PLANTS 
| ANGIOSPERMS or } PLANTS 
seed-plants with Suspciass II 
closed ovaries DICOTYLEDONOUS 
PLANTS 
- 256. The Groups of Cryptogams. — The student is not 
to suppose that the arrangement of cryptogams into the 
four great groups given in the preceding table is the only 
way in which they could be classed. It is simply one 
way of dividing up the enormous number of spore-bearing 
plants into sections, each designated by marked character- 
istics of its own. But the amount of difference between 
one group and another is not always necessarily the same. 
The pteridophytes and the bryophytes resemble each 
other much more closely than the latter do the thallo- 
phytes, while the myxothallophytes are but little like other 
plants and it is extremely probable that they are really 
animals. 
The classes given in the table do not embrace all known 
cryptogams, but only those of which one or more repre- 
sentatives are described or designated for study in this 
book. Lichens in one sense hardly form a class, but it is 
most convenient to assemble them under a head by them- 
selves, on account of their extraordinary mode of life, a 
partnership between alge and fungi. 
257. The Classes of Seed-Plants. — The gymnosperms 
are much less highly developed than other seed-plants. 
