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- 



FiG. 14. — The cinnamon fern {Osmiinda 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 



