222 PLANT STUDIES 
constant termination phytes, 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 Algm 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. 
149. 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., 
