74 



FLOWERS. 



[SECTION 8. 



raceme are of course the oldest, and therefore open first, and the order of 

 blossoming is ascending from the bottom to the top. The summit, never 

 being stopped by a terminal flower, may go on to grow, and often does 

 so (as in the common Shepherd's Purse), producing lateral flowers one 

 after another for many weeks. 



206. A Corymb (Fig. 202) is the same as a raceme, except that it i& 

 flat and broad, cither convex, or level-topped. That is, a raceme becomes 

 a corymb by lengthening the lower pedicels while the uppermost remain 



shorter. The axis of a corymb is short in proportion to the lower pedicels. 



By extreme shortening of the axis the corymb may be converted into 

 207. An Umbel (Fig. 203) as in the Milkweed, 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. 



208. The corymb and the umbel being more or less level- 

 topped, bringing the flowers into a horizontal plane or a con- 

 vex form, the ascending order of development appears as Cen- 

 tripetal. That is, the flowering proceeds from the margin or 

 circumference regularly towards the centre ; the lower flowers 

 of the former answering to the outer ones of the latter. 



209. In these three kinds of flower-clusters, the flowers art, 

 raised on conspicuous pedicels (204) or stalks of their own. The 

 shortening of these pedicels, so as to render the flowers sessilb 

 or nearly so, converts a raceme into a Spike, and a corymb or an 

 umbel into a Head. 



210. A Spike is a flower-cluster with a more or less length- 

 ened axis, along which the flowers are sessile or nearly so ; as in 

 the Plantain (Fig. 201). 



211. A Head (Capitulum) is a round or roundish cluster of flowers, 



204 



Fro. 201. A raceme. 202. A corymb. 203. An umbel. 

 Fig. 204. Spike of the common Plantain or Ribwort. 



