142 



PARTICULAR FORMS OF FLOWERS 



are perfect and have four sepals. The common calla lily 

 is a good example of this type of inflorescence. 



281. COMPOSITOUS FLOWERS. The head (anthodium) 

 or so-called "flower" of sunflower (Fig. 177), thistle, aster 



MklMtfL, ( Fi - 227 )' dandelion, daisy, 



chrysanthemum, golden -rod, -is 

 composed of several or many 

 Uttle flowers, or florets. These 

 florets are inclosed in a more 

 or less dense and usually green 



228. Head of pasture thistle, showing 

 the high prickly involucre. 



229. Longitudinal section 

 of thistle head. 



230. Floret of 

 thistle. 



involucre. In the thistle (Fig. 228) this involucre is 

 prickly. A longitudinal section (Fig. 229) discloses the 

 florets, all attached at bottom to a common torus, and 

 densely packed in the involucre. The pink tips of these 

 florets constitute the showy part of the head. 



282. Each floret of the thistle (Fig. 230) is a complete 

 flower. At a is the ovary. At & is a much -divided plumy 

 calyx, known as the pappus. The corolla is long -tubed, 

 rising above the pappus, and is enlarged and 5-lobed at 



