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 CHAPTER XXIII

PHENOGAMS AND CRYPTOGAMS

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 produce no seeds, and these plants (including bacteria) 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.

—Dryopteris acrostichoides; known also as Aspidium.

Sori at a. One sorus with its indusium at b.

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),