THE COMPOSITOUS TBI B JUS 



181 



This is 



clothing in a walk through a weedy field. He 

 will soon be prepared to say that the pappus may 

 be either absent or very abundant, and may vary 

 in character from a narrow rim on the top of the 

 seed -like body to scales, barbs, bristles and plumes. 



207. The disc floret in Fig. 173 has another 

 peculiarity in the presence of a scale {a). 

 present in many compositous flowers, 

 and, like nearly all scales, is homol- 

 ogous with a leaf ; one of these 

 scales subtends each floret, and thereby^ 

 we have another proof that the re- 

 ceptacle of a composite head is really 

 a shortened branch, or a rachis. 



207a. The pupil will now appreciate the teasel. 

 One form of it is common along roadsides in the 

 Eastern states. The flower-head would pass at 

 once for a composite, but the anthers are not 

 syngenesious, and there are other technical differ- 

 ences; so that the teasels are not classed with 

 compositous plants, although closely allied to them. The fuller's 

 teasel (Fig. 174) is remarkable for the enormous development of the 

 scales; and after the flowers have perished, the dry head is used 

 for raising the nap on woolen cloth. The plant is cultivated 

 in central New York for this purpose. 



208. Another important contrast of the rudbeckia 

 and the dandelion is to be found in the invo- 

 lucre. In each case the scales or bracts of the 

 involucre are approximately in two rows, but in the 

 rudbeckia the two rows occupy the same position. 



Fig. 175. 

 Floret of aster. 



