2 PLANT STRUCTURES 



constant termination pliytes, which is a Greek word mean- 

 ing " plants." The prefix in each case is also a Greek word 

 intended to indicate the kind of plants. 



(1) Thallophytes. The name means "thallus plants," 

 but just what a "thallus" is can not well be explained 

 until some of the plants have been examined. In this 

 great group are included some of the simplest forms, 

 known as AlgcB and Fungi, the former represented by green 

 thready growths in fresh water and the great host of sea- 

 weeds, the latter by moulds, mushrooms, etc. 



(2) Bryophytes. The name means " moss plants," and 

 suggests very definitely the forms which are included. 

 Every one knows mosses in a general way, but associated 

 with them in this great group are the allied liverworts, 

 which are very common but not so generally known. 



(3) Pteridophytes. The name means " fern plants," and 

 ferns are well known. Not all Pteridophytes, however, are 

 ferns, for associated with them are the horsetails (scouring 

 rushes) and the club mosses. 



(4) Spermatophytes. The name means " seed plants " 

 that is, those plants which produce seeds. In a general 

 way these are the most familiar plants, and are commonly 

 spoken of as " flowering plants." They are the highest in 

 rank and the most conspicuous, and hence have received 

 much attention. In former times the study of botany in 

 the schools was restricted to the examination of this one 

 group, to the entire neglect of the other three great groups. 



3. Increasing complexity. At the very outset it is well 

 to remember that the Thallophytes contain the simplest 

 plants those whose bodies have developed no organs for 

 special work, and that as one advances through higher 

 Thallophytes, Bryophytes, and Pteridophytes, there is a con- 

 stant increase in the complexity of the plant body, until in 

 the Spermatophytes it becomes most highly organized, with 

 numerous structures set apart for special work, just as in the 

 highest animals limbs, eyes, ears, bones, muscles, nerves, etc.. 



