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 insects are used ; and in passing from Gym- 

 nosperms to Angiosperms one passes from anemophilous to 

 entomophilous ("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 floral leaves are pecul- 

 iar to Angiosperms, making the true 

 bane (Hyoscyamus) : A, flower, and being associated with en- 

 tomophily. 



110. Microsporophylls, The micro- 

 sporophyll of Angiosperms is more 

 definitely known as a " stamen " than 



A W wjf 



FIG. 165. Stamens of hen- 



ment (/) and anther (/>); 

 B, back view, showing 

 the connective (c) be- 

 tween the pollen-sacs. 

 After SCHIMPEK. 



