12 



HEREDITY AND EVOLUTION IN PLANTS 



equal degree, as in the case of Polypodium mentioned 

 above. In some species, however, there are two kinds of 

 leaves one devoted entirely to vegetative functions, and 

 another to the reproductive, or spore-producing function 

 (Fig. 14); between these two extremes all grades of transi- 

 tion are found (Fig. 15). But however widely the sporo- 



Fic. 14. The cinnamon fern (Osmunda cinnamomea) , showing foliage 

 leaves and sporophylls. 



phyll departs from a foliage-leaf in appearance, it must, 

 nevertheless, be regarded as morphologically a leaf. As 

 partial evidence of the true foliar nature of sporophylls, 

 there may be cited the interesting experiment of Atkinson, 

 who, by removing the true foliage-leaves just beginning to 

 unfold in the spring, was able to induce developing sporo- 

 phylls to alter their character, and become transformed 



