74 



FOUNDATIONS OF BIOLOGY 



FIG. 39. The Sensitive Fern (Onoclea 

 sensibilis), showing vegetative leaf, and 

 spore leaf, or sporophyll, arising from the 

 rhizome. (From Bergen and Davis.) 



bearing structures of Ferns 

 and Flowering Plants. In 

 some Ferns the spore cases 

 (sporangia) are borne upon 

 typical leaves, while in others 

 they arise on special leaves 

 with chlorophyll-bearing 

 tissue partly or completely 

 suppressed. Such leaves 

 which are given over to the 

 production of spores, as in 

 the Sensitive Fern, are known 

 as SPOROPHYLLS. (Fig. 39.) 

 In the Flowering Plants, the 

 FLOWER is a group of sporo- 

 phylls, known as CARPELS 

 and STAMENS, associated in 

 most cases with certain sterile 

 leaf structures, termed SE- 

 PALS and PETALS, which af- 

 ford protection to the sporo- 

 phylls and offer attraction to 

 insect visitors. (Figs. 40, 58.) 

 We shall consider the 

 structure of the flower in 

 more detail in discussing re- 

 production in plants, but it 

 is essential now, having con- 

 sidered the fundamental di- 

 visions (root, stem, and leaf) 

 of the body of vascular 

 plants, and some of the adap- 

 tive modifications of these 



