12 



BOTANY: PRINCIPLES AND PROBLEMS 



developed w>xual structures and their more complicated methods 

 of reproduction. The plant body of the Bryophytes has no roots, 

 and in many cases consists of only a flat, strap-like mass of green 

 tissue, but the higher members of the group possess very simple 

 stems and leaves. The plants are small and inconspicuous, 

 and generally thrive best in moist situations. Bryophytes are 

 subdivided into the simple and lowly Liverworts (Hepaticae) and 

 the commoner and more highly specialized Mosses (Musci, Fig. 6). 



Fig. 4. — An Alga. One of the rock-weeds {Fucus spiralis) growing on a rock 

 between tide-marks. {Photo by M. A. Howe). 



C. The Pteridophytes or Fern Plants.— These possess true 

 roots, stems, and leaves, essentially similar in structure to those 

 of the Seed Plants, but they still reproduce by spores rather than 

 by seeds. Compared with Bryophytes, the plant body is large 

 and vigorous, and it is well adapted to life on land. The three 

 important subdivisions of the Pteridophytes are: The Ferns 

 (Filicales, Fig. 7), possessing large and feathery leaves on the 

 backs of which the spores are produced; the Club Mosses or Ground 

 Pines (Lycopodiales), which have spore-bearing cones, solid 

 stems and scale-like, spirally arranged leaves; and the Horsetails 

 (Equisetales) also possessing cones but with jointed, hollow stems 

 and minute, whorled leaves. 



