386 
The Ohio Naturalist. 
[Vol. VI, No. 1, 
THE CLASSIFICATION OF PLANTS, II. 
John H. Schaff.ner. 
The three series of plants (Thallo])hyta, Archej^oniata, and 
Spermatophyta) fall into smaller groups which also represent a 
succession of higher and higher stages of progressive develop- 
ment. If the theory of evolution as accepted at present is .sub- 
stantially correct, it becomes evident that some forms of plant 
life remained in the lowe.st condition from the beginning while 
others advanced to higher and more complex stages. Why did 
large numbers of species develop and continue until the ])resent 
time without advancing to any apprecialde extent from the 
starting point? The question can be answered by assuming 
that groups of organisms varied and were specialized in a direc- 
tion which interfered with further progress upward but not with 
further variation along subordinate lines. Other grou])s varied 
in a direction which led to higher possibilities without imposing 
a barrier while still others passed back from a higher to a lower 
condition. 
Based on the conception of vertical or progressive evolution, 
the develo]:)ment of the ])lant kingdom may be arranged some- 
what as follows: 
1 . Genesis of living organisms. 
2. Primordial organisms or Archeophyta, supposed to have 
been naked, amoebid cells of the simplest structure. 
3. Transition to encysted and wall cells of the types found 
in the lowest jjlants of the present time. 
4. Xonsexual plants consisting of simple cells, masses, or 
filaments. 
.'). Development of .sexuality or of conjugating organisms. 
(). The lower types of sexual plants. 
7. Gradual development of the higher and more complex 
types, manv with a simple alternation of generations. 
5. The higher Thallophytes. 
9. Transition to tyjiical land plants and adaption to aerial 
conditions. 
10. The lowest ]ilants with a ty]hcal antithetic alternation 
of generations and with a simple parasitic sporojihyte. 
1 1 . Gradual development of a more complex sporophyte. 
12. The higher plants with a well develo]>ed dependent 
sporophyte. 
13. Transition to plants with an independent mature 
sporophyte. 
14. Plants with homosporous .sporo])hytes with true roots, 
leaves, and fibro-vascular tissue. 
b”). Development of heterospory. 
