DEVELOPMENT OF PLANTS 



419 



about the nut is finally destroyed by decay, while in the hickories 

 the rind becomes leathery and splits into valves, freeing the nut 

 (Fig. 301, C). 



The order of the nettles, Urticales, also has many points in 

 common with the beech order and contains several of our com- 

 mon trees as the elm {Ulmus, Fig. 302), hackberry (Celtis), mul- 

 berry (Morns), osage orange (Toxylon), numerous tropical 

 forms, as the India rubber trees, banyan tree, etc., as well as 



Fig. 299. 



Fig. 300. 



Fig. 299. The beech family, order Fagales: A, inflorescence of oak (Quer- 

 cus) — s, staminate ament: p, pistillate inflorescence. B, staminate flower 

 surrounded by a perianth of slightly united bracts. C, pistillate flowers 

 with numerous bracts surrounding base of ovary. D, section of flower, the 

 pistil being composed of three carpels and the inner bracts adnate to the 

 ovary. E, fruit of oak, the cup consisting of the modified outer bracts shown 

 in C and D and the nut has developed from the ovary and one of its ovules. 



Fig. 300. Flower and fruit of the beech (Fagus), order Fagales: A, pis- 

 tillate inflorescence, the three-lobed stigmas projecting beyond the bracts. 

 B, section of the inflorescence — pr, inner bracts or perianth surrounded by 

 an outer spiny set. C, the fruit, the outer bracts of B have become hard 

 and spiny and are splitting into four valves, exposing the three-angled nuts. 



