252 



ELEMENTARY SCIENCE 



round cells escape. Each one of them, if it reaches a favor- 

 able place, will produce a liverwort-plant. These little 

 round reproductive cells are called spores. Spores are repro- 

 ductive cells that can grow directly into new plants. Eggs 

 and sperms are cells that cannot grow directly into new 

 plants; they must unite before the new plant is produced. 



Mosses look more 

 like regular land-plants 

 than liverworts do, but 

 you nearly always find 

 mosses where you find 

 liverworts, and they 

 have the same method 

 of reproduction. They 

 belong to the same 

 great group of plants 

 (see Fig. 92). 



The fourth step to- 

 ward seeds is repre- 

 sented by ferns. You 

 all know ferns. Have 

 you ever noticed that 

 sometimes you find on 

 the under surface of 

 fern-leaves many small 



brown structures ? (See Fig. 93.) These brown structures 

 are made up of many little cases, and each one of the 

 cases contains spores. Ferns do not have seeds. For their 

 spreading abroad over the land they have to depend upon 

 these spores. But you can see that these tiny spores have 

 many disadvantages as compared with seeds. They are 

 not protected by a thick wall and -they do not contain 



FIG. 93. Maidenhair fern with brown spore 

 cases at the edges of the leaves. 



