HEREDITY AND EVOLUTION IN PLANTS 



into foliage-leaves. Similar results were also obtained by 

 Goebel. These experiments indicate that foliage-leaves 

 and sporophylls are very closely related to each other, 



FIG. 16. Portion of a leaf of a fern (Tectoria cicutaria) that bears 

 bulbils on both the upper and lower surfaces of its leaves. Plantlets 

 develop from the bulbils while they are still attached. 



and demonstrate clearly that foliage-leaves may be pro- 

 duced by the sterilization of spore-bearing leaves. The 

 interesting question here naturally arises as to whether, in 

 the evolutionary development of the plant kingdom 



