FLOWERS AND THEIR USES 265 



pedicels may vary much in length, and these variations re- 

 sult in flower clusters of different forms. 



One of the simplest kinds of clusters is the raceme, in which 

 both the peduncle and the pedicels are fairly long and all 

 the pedicels are of about the same length. The lily-of-the- 

 valley, the bean, and the currant have their flowers in 

 racemes. In a spike, such as that of the plantain or of the 

 mullein, the pedicels are so short that the flowers are very 

 close to the peduncle, and the peduncle is shortened enough 

 to bring the separate flowers close together. A catkin is 

 much like a spike, excepting that it droops. The flower 

 clusters of willows and of a good many other trees and 

 shrubs are catkins. In a corymb, like that of a hawthorn, 

 the peduncle is shortened ; the pedicels are of unequal 

 length, so that all the flowers are borne at about the same 

 level and the cluster is more or less flat-topped. In a corymb 

 the flowers that come from the lower part of the peduncle 

 are the first to open. A cyme is like a corymb, excepting 

 that the flower at the end of the peduncle (the central flower 

 of the cluster) opens first, and those borne lower down on 

 the peduncle open later. The flower clusters of pears and 

 apples are small cymes. In an umbel, such as that of the 

 cherry, the peduncle is so much shortened that all the pedi- 

 cels arise at the same level. They are also of' about the 

 same length, so that an umbel, like a corymb, is flat-topped. 



In a head, both peduncle and pedicels are much short- 

 ened, so that all the flowers are at about the same level and 

 are very closely packed together. The heads of the red 

 clover are familiar. So are those of the members of the 

 composite family, including the sunflower, the dandelion, 

 and the thistle. The flowers of composites are so closely 

 packed together that the head is thought of by most people 

 as a single flower. This notion is helped by the fact that 

 the outer flowers of the head are often (as in the sunflower 

 and the daisy) different from the inner ones and look like 



