74 



FLOWERS. 



[SECTION -8. 



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

 blossoming *s 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. 



20G. A Corymb (Fig. 202) is the same as a raceme, except that it is 

 flat and broad, either 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 aud 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 are 

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

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

 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 



m the Plantain (Fig. 204). 



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



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

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



