A MANUAL OF BOTANY 157 



Class I. Hepattcs, or Licerworts. Flattened horizontal 

 thallus forms or mosslike. 



Class II. Mosses proper^ with two subclasses. 



A. Ordinary mosses, mostly terrestrial or arboreal, some 



aquatic. 



B. Sphagnum forms, aquatic. Peat producers. 



Branch III. Pteridophytes, or Fern Plants.^ 



Green plants, mostly leafy, commonly with un- 

 derground stems ; marked alternation of gen- 

 erations and complicated spore production. 



Class I. Ferns. Several thousand species of fernlike 

 aspect. 



Class II. Horsetails and scouring rushes. 



Green, hollow, jointed stems and scale leaves; 

 conelike spore structures. 



Class III. Club mosses. Mosslike plants with conelike 

 spore fruits. 



Branch IV. Spermatophytes, or Seed Plants. 



Plants with so-called flowers and seed pro- 

 duction. 



Class I. Gymnosperms, or naked seeds ; narrow or scale 

 leaves (usually), mostly evergreen; pines, 

 spruces, cedars, yews, — big trees. 



(Jlass II. Angiosjyerms, or covered seeds; vastly im})or- 

 tant. 

 Ordinary flowering plants of two subclasses; 



A. Monocotyledons, or one-seed le<(f; grasses, lilies, iris, 



orchids, etc. 



B. Diocotyledons, or two-seed leaves; pinks, crowfoots, 



mustards, roses, peas, and hosts of others. 



1 Onl}' the more important classes are named. 



