326 



A TEXTBOOK OF BOTANY [Ch. VI, 10 



of the flower, the prothallial cells 

 of both embryo sac and pollen 

 grain, together with egg cell and 

 sperm cell belong to a new gen- 

 eration. 



These morphological matters 

 are certainly complicated and 

 difficult at first to grasp in detail! 

 They can be made clearer, how- 

 ever, by aid of a table or dia- 

 gram which will exhibit their 

 relations in light of their evolu- 

 tionary origin, and of the con- 

 nections of the reproductive with 



the nutritive parts; and such a diagram is presented on 



the opposite page. 



We have now traced the flower back to its morphological 



Fig. 224. — Sorus of a fern, 

 in cross section, showing the 

 stalked sporangia containing 

 spores ; magnified. From these 

 spores there is an unbroken 

 series to the embryo sacs and 

 pollen grains of flowers. (From 

 F. Darwin.) 



/ / o o \ \ / / <? *> \ \ 







i i 



\ \ • o . 





Fig. 225. — Plans, or diagrams, of typical flowers, to illustrate presence 

 and absence of the whorls. 



They represent cross sections supposed to be made through the widest 

 parts of sepals, petals, stamens, and pistil. Above, the first is a complete 

 flower (Staphylea), and the second is apetalous (Beet). Below, the first is 

 asepalous and apetalous (Saururus), the next is staminate only (Willow), and 

 the last is pistillate only (Willow) . 



