DEVELOPMENT OF PLANTS 



477 



FIG. 331. 



FIG. 332. 



FIG. 331. A common species of the mint family: A, inflorescence of the 

 skull cap (Scut ell aria) . Note the square stem, opposite leaves. Why are 

 all the flowers facing one way? B, flower enlarged, showing the two-lobed 

 under lip and the three-lobed upper lip which conceals the sporophylls. C, 

 section of the flower. Ovary four-lobed, stamens cohering with the corolla 

 and anthers concealed with the stigma beneath upper lip. Purpose of the 

 crest, c, on the calyx? 



FIG. 332. Flower of the sage (Salvia): A, flower after the anthers have 

 shed their spores. The two-lobed stigma is bending down into the position 

 occupied by them. B, sectional view of the flower, showing four-lpbed ovary 

 with nectar glands at the base, stigma not receptive and bent back. As the 

 insect enters the flower he pushes against the sterile lobe of the anther, /, and 

 thus causes the fertile lobe, a, to swing down upon his back. /, filament of 

 anther. 



