LESSON ll.j RACEMKj CORYMB, UMBEL, ETC. 



79 



by intermediate gradations of every sort. For instance, if we 

 lengthen the lower pedicels of a raceme, and keep the main axis 

 rather short, it is converted into 



203. A Corymb (Fig. 158). This is the same as a raceme, except 

 that it is flat and broad, either convex, or level-topped, as in the 

 Hawthorn, owing to the lengthening of the lower pedicels while the 

 uppermost remain shorter. 



204. ^he main axis of a corymb is short, at least in comparison 

 with the lower pedicels. Only suppose it to be so much contracted 

 that the bracts are all brought • into a cluster or circle, and the 

 corymb becomes 



205. An Umbel (Fig. 159), — as in the Milkweed and Primrose, 

 — a sort of flower-cluster where the pedicels all spring apparently 

 from the same point, from the top of the peduncle, so as to resemble, 

 when spreading, the rays of an umbrella, whence the name. Here 

 the pedicels are sometimes called the rays of the umbel. And the 

 bracts, when brought in this way into a cluster or circle, form what 

 is called an involucre. 



206. For the same reason that the order of blossoming in a ra- 

 ceme is ascending (201), in the corymb and umbel it is centripetal, 

 that is, it proceeds from the margin or circumference regularly to- 

 wards the centre ; the lower flowers of the former answering to the 

 outer ones of the latter. Indeterminate inflorescence, therefore, is 

 said to be centripetal in evolution. And by having this order of 

 blossoming, all the sorts may be distinguished from those of the 

 other, or the determinate class. In all the foregoing cases the 

 flowers are raised on pedicels. These, however, are very short in 

 many instances, or are wanting altogether; when the flowers are 

 tessile (200). They are so in 



FIG. 157. A raceme. 1S8. A coryqjj), 159. An umbel. 



