PROBLEM 2. The Kinds of Vlants of the Earth 



79 



Fig. 103 The bay-scented fern. Not all jerns 

 have leaves {fronds) as finely divided as this. 



(SCHNEIDER AND SCHWARTZ) 



PHYLUAI - PTERIDOPHYTES 



Ferns and Their Relatives 



The third large division — the ferns. 



There is something about a fern that 

 pleases the eye; for that reason you have 

 all noticed ferns. They have been culti- 

 vated, too, so that they are often seen 

 in homes. There are almost four thou- 

 sand different species growing in many 

 parts of the world. Most species need 

 moisture and thrive best in the shade of 

 forest trees. But some, like the sensitive 

 fern, live on the edge of the forest; a few, 

 like the bracken or brake, grow in sunny 

 fields. Alost fern leaves (called frojids) 

 are divided and often finely subdivided 

 into leaflets. The leaf comes up from 

 the ground tightly coiled like a flddle- 



FiG. 104 The ^^scouring nisb" is a relative of the 

 fern. It is harsh and gritty to the touch. (Brook- 

 lyn BOTANIC garden) 



head; as it grows, it uncoils and spreads 

 out its broad surface. In most ferns the 

 leaves are the only parts that are visible; 

 the woody stem lies underground and 

 may extend for many feet just under- 

 neath the surface of the soil. Like all 

 the plants you have read about so far 

 ferns never form flowers or seeds. 



In the tropics ferns grow to a much 

 greater size and some develop strong 

 stems above ground. In fact they may 

 grow as trees sixty or more feet high. 

 And there was a time some 200 million 

 years ago or more when large tree ferns 

 grew in vast numbers much farther north. 



