626 



BOTANY OF CROP PLANTS 



Inflorescence. — The inflorescence (Fig. 254, A) is a head, 

 the flowers, usually numerous, being mounted on a common 

 receptacle which is subtended by an involucre. A "sun- 

 flower" is not a single flower in the botanical sense, but a 

 group or composite of individual flowers. The receptacle 



wiers 



bracts 

 recepiacie 



ovary wall 

 <vule 



Fig. 254. — Jerusalem artichoke (Helianthus tuberosus). A, lengthwise 

 section of head. X i ; B, ray flower, X 6; C, disk flower, cut lengthwise, X 6. 

 (A after Baillon.) 



varies in shape from flat to convex or conical. The recep- 

 tacle is naked or there are chaffy scales subtending the flower; 

 its surface is smooth, pitted, or honeycombed. The involu- 

 cral bracts also vary widely in shape, from narrow and spine- 

 like to broad and leaf -like; they occur in one or more series. 



