CHAPTER XXIII 



PHENOGAMS AND CRYPTOGAMS 



The plants thus far studied produce flowers ; and the 

 flowers produce seeds by means of which the plant is prop- 

 agated. There are other plants, 

 however, that produce no seeds, 

 and these plants (including bac- 

 teria) are probably more numer- 

 ous than the seed-bearing plants. 

 These plants propagate by means 

 of spores, which are generative cells, 

 •usually simple, containing no em- 

 bryo. These spores are very small, 

 and sometimes are not visible to 

 the naked eye. 



Fig. 254. — Christmas Fern. 

 — Dryopteris acrostichoides ; 

 known also as Aspidium. 



Prominent among the spore- 

 propagated plants are ferns. The 

 common Christmas fern (so called 

 because it remains green during 

 winter) is shown in Fig. 254. The 

 plant has no trunk. The leaves 

 spring directly from the ground. 

 The leaves of ferns are called 

 fronds. They vary in shape, as 

 other leaves do. Some of the 

 fronds in Fig. 254 are seen to be 

 narrower at the top. If these are 

 examined more closely (Fig. 255), 



176 



Fig. 255. — Fruiting FtoND 

 OF Christmas Fern. 



Sori at a. One sorus with its in- 

 dusium at b. 



