THE STORY OF SEEDS 



251 



plants are protected from drying up by a covering through 

 which water does not easily evaporate. So the plants 

 that first lived on 



FIG. 91. Pot of liverworts, the first land-plants. 



the land had to de- 

 velop a kind of cover- 

 ing that their water- 

 dwelling ancestors did 

 not need. 



To-day we find 

 growing in damp 

 places certain flat 

 little plants that look 

 as though they had 

 rather recently come 

 out of the water, and 

 are just learning to 

 live on the land. These plants are called liverworts, and 

 their favorite home is in moist and shady places, especially 

 on damp cliffs (see Fig. 91). These plants 

 show us the third step in our story. They pro- 

 duce eggs and sperms, and the sperms swim 

 just as they do in algae. But the eggs stay where 

 they are formed. The sperms have to come to 

 them. The union of the egg with the sperm is 

 called fertilization. The cell that results from 

 union of egg and sperm is called the fertilized 

 egg. Now right here is the new point in the 

 story. The fertilized egg does not grow into a 

 plant like its parent. It grows into a club- 

 shaped structure, and this structure contains 

 'p'u'n t s hundreds of very small round cells. Presently 

 cS5si. M ' the wall of this structure bursts and the small 



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