CHAPTER XXVI 



PHENOGAMS AND CRYPTOGAMS 



344. The plants thus far studied produce flowers; and 

 the flowers produce seeds by means of which the plant is 

 propagated. There are other plants, however, that pro- 

 duce no seeds, and these plants are probably more numerous 

 than the seed-bearing plants. These plants propagate by 

 means of spores, which are generative cells, usually simple, 

 containing no embryo. These spores are very small, and 

 sometimes are not visible to the naked eye. 



345. Prominent amongst the spore-propagated plants 

 are ferns. The common Christinas fern (so called because 

 it remains green during winter) is shown in Fig. 331. The 

 plant has no trunk. The leaves spring directly from the 

 underground stem. The leaves of ferns are called fronds. 

 They vary in shape, as other leaves 

 do. Compare Fig. 139 and the 

 pictures in this chapter. Some of 

 the fronds are seen to be narrower 

 at the top. If these are examined 

 more closely (Fig. 332) it will be 

 seen that the leaflets are contracted 

 and are densely covered beneath 

 with brown bodies. These bodies 

 are collections of sporangia or spore- 

 cases (singular, sporangium). 



346. The sporangia are collected into little groups, 

 known as sort (singular, sorus) or fruit-dots. Each sorus is 

 covered with a thin scale or shield, known as an indusium. 

 This indusium separates from the frond at its edges, and the 



(179) 



331. Christmas fern. — Dryopteris 

 acrostichoides; known also aa 

 Aspidium. 



