THE AMERICAN NATURALIST [Vol. XLIII 



and sometimes this form is attained even in very old 

 plants, especially those growing in the quieter places, but 

 usually the stipes twist more or less and spread out in all 

 directions, giving the plant a tree-like aspect. 



There is no change in this habit of growth until the 

 plant has attained a considerable age. But long before it 

 reaches its full size there appears another kind of lamina 

 among the narrow ones with midribs. These lack the 

 midribs and are much wider, with conspicuously rounded 

 or subcordate bases. The ribbed laminae are always 

 sterile, but these wider ones become sporophylls. Con- 

 sequently after their sporangia are discharged they 

 slough off and disappear, leaving for a time scars on the 

 stipe. The origin of these sporophylls is evidently dif- 

 ferent from that of the ordinary laminae. Since very few 

 new sporophylls are developed during the summer, at 



