l62 



THE POPULAR SCIENCE MONTHLY. 



Fig. 6 is seen a vertical section of one fully grown, showing the vari- 

 ous parts of theca, calyptera, operculum, etc. In this comi^licated 

 sporangium, small spores in great numbers are produced, and with 

 their perfection ends the last chapter in the life-history of the moss. 



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Fig. 4. 



The spore produces a fine filamentous growth, from which the true 

 moss-plant develops. This is the sexual generation, and from ferti- 

 lized germ-cells, which it bears, the asexual generation is produced, 

 consisting of the spore-case, its stalk, and, most important of all, the 

 many spores. 



We now come to a more exalted group of plants, and the first of 

 the cryptogams with spiral vessels and other ducts in the wood. The 

 ferns are so familiar to all that any description of their general appear- 

 ance is unnecessary. The first generation proceeds directly from the 

 spore, and consists of a simple green expansion which is short-lived and 

 very small, not usually exceeding half the size of a small finger-nail. 

 This prothallus, as it is termed, has small, root-like hairs which fix it 

 to the earth or elsewhere. The prothallia are to be seen in large num- 

 bers on the sides of flower-pots in neglected greenhouses. Each little 

 green scale is a young fern-plant during its sexual generation. The 

 male and female organs are much the same shape as those of mosses. 



