54 EASY LESSONS IN VEGETABLE BIOLOGY. 



nearer the base, but in the fern the frond grows as 

 the stem does, so that the peduncle, or stalk, is first 

 formed, then the embryo frond, then the pinnules, or 

 wings, etc. 



Underneath the frond of a fern we may sometimes 

 see little brown patches. Each patch is called a sorus, 

 (plural, sori.) It is sometimes covered by a mem- 

 brane called an indusium, and the little brown bodies 

 constituting it are spore-cases which have been de- 

 veloped from epidermal cells. An elastic ring sur- 

 rounds each spore-case and assists in opening it. The 

 growth of the minute spores in the spore-cases may be 

 watched from time to time under the microscope. 

 The little spore swells and bursts, and sends out a 

 rootlet into the soil. Then a number of delicate cells 

 are formed from the mother-cell in the spore, making 

 a little green scale, which throws out rootlets on its 

 under side. This protliallium (as it is called) pro- 

 duces two kinds of cells, one set which contains spiral 

 filaments which escape and, by apparently spontane- 

 ous movements enter the others, or germ-cells, from 

 which the future fern is produced. Fig. 24 gives 

 a good representation of the various parts in the 

 structure and life-history of a fern. 



3. Mosses are also examples of plants which grow 

 at the tip, or summit. They are minute and lowly 

 plants, but are by no means insignificant. They have 

 distinct axes of growth, and their delicate leaves are 



