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 mauy weeks. 



206. A Corymto_,(rig. 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 (F'g- 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 

 Rayt of the umbel. And the bracts, when brought in this way 

 into a cluster or circle, form what is called an Involucke. 



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 tlie 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 



'^ the Plantaift (Fig. 204). 

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



Fio. 201. A raceme. 202. A corymb. 20a An umbel. 

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



