How Plants Perpetuate Their Kinds 



289 



step in the development of such secondary sexual structures is 

 found even in the higher Seaweeds (the Red Algae), in which the 

 egg-cell is not cast loose, as in the lower forms, but remains at- 

 tached to the parent plant that forms it and supplies its store of 

 nourishment; while simple arrangements exist to facilitate the 

 access of the male cell. ' But far more important is the step taken 



-' 





FIG. 103. A series of figures illustrating the reproduction of the common Rockweed. In 

 the middle lower part is the spherical female (egg) cell, highly magnified, surrounded 

 by a number of the very much smaller free-swimming male (sperm) cells. 



in the simplest land plants, like the lowly Liverworts and Mosses, 

 and the fertilization stage of the Ferns, i. e., a stage in which the 

 plant is a tiny thin leaf pressed close to the ground. In all of these 

 plants the very delicate egg-cell and the subsequent embryo need 

 protection from the dryness to which they must occasionally be 

 exposed, and a protection, of course, which does not interfere 



