196 



PLANT STRUCTURES 



elaborate symbiotic relation between flowers and insects, 

 through which pollination is secured. In Angiosperms, 

 therefore, the wind is abandoned as an agent of pollen 

 transfer and i nsects are used ; and in passing from Gym- 

 nosperms to Angiosperms one passes from anemophilous to 

 entomopMlous ("insect-loving") plants. This does not 

 mean that all Angiosperms are entomophilous, for some are 

 still wind-pollinated, but that the group is prevailingly ento- 

 mophilous. This fact, more than anything else, has re- 

 sulted in a vast variety in the structure of flowers, so char- 

 acteristic of the group. 



109. The plant body. — This of course is a sporophyte, 

 the gametophytes being minute and concealed, as in Gym- 

 nosperms. The sporophyte represents the greatest possible 

 variety in habit, size, and duration, from minute floating 

 forms to gigantic trees ; herbs, shrubs, trees ; erect, pros- 

 trate, climbing ; aquatic, terrestrial, epiphytic ; from a few 

 days to centuries in duration. 



Eoots, stems, and leaves are more elaborate and vari- 

 ously organized for work than in other groups, and the 

 whole structure represents the high- 

 est organization the plant body has 

 attained. As in the Gymnosperms, 

 the leaf is the most variously used 

 organ, showing at least four distinct 

 modifications : (1) foliage leaves, (2) 

 scales, (3) sporophylls, and (4) floral 

 leaves. The first three are present 

 in Gymnosperms, and even in Pteri- 

 dophytes, but floralj eaves are pec ul- 

 iar to Ang iosperms, making the true 

 flower, and being associated with en- 

 tomophily. 



110. Microsporophylls. — The micro- 

 sporophyll of Angiosperms is more 

 definitely known as a " s tamen. " than 



Fig. 165. Stamens of hen- 

 bane (Hyoscyamus) : A, 

 front view, showing fila- 

 ment (/) and anther (p); 

 B, back view, showing 

 the connective (c) be- 

 tween the pollen-sacs. 

 —After Schimpkr. 



