Classification of Plants 



221 



scope, and are consequently so unfamiliar to those for whom 

 this book is intended that they can be but briefly mentioned. 



Division I. — Thallophyta. 



This division includes a great variety of plants, some very 

 simple and others quite elaborate, but they are grouped together 





Fig. 195. — Vaucheria. A, B, formation of antheridia and oogonia ; /z, male 

 branch ; a, antheridium ; og, oogonium ; C, oogonium opening to exude the 

 drop of mucilage, si ; D, spermatozoids ; E, spermatozoids entermg oogonium ; 

 F, a, an empty antheridium ; osp, oogonium with oospore or fertilized oosphere 

 (magnified). (After Goebel and Pringshein. ) 



as having no root, stem or leaves, and in having one-celled fruiting 

 organs. It may be divided into three subdivisions. 



A. Alg/f:. — Most of the plants composing the green floating 

 scum on ponds, which is sometimes called " frog spittle," are algae. 

 Others are found on damp walls, on stones, or moist earth. All 

 the seaweeds are algae. These plants may be but single cells, 

 long threads or filaments of cells, or masses of cells. The fila- 

 ments may break apart, and so form new plants, or the cell 



