132 



ELEMENTS OP BOTANY. 



The Raceme and Related Forms. — If the leaves along the 

 stem -were to become very much dwarfed and the flowers 

 brought closer together, as they frequently are, a kind of 

 flower-cluster like that of the currant (Fig. 105) or the lily of 

 the valley would result. Such an' inflorescence is called a 

 raceme; the main flower stalk is known as the peduncle ; the 

 little individual flower stalks are pedicels, and the small, more 

 or less scale-like leaves of the peduncle are bracts} 



Frequently the lower pedicels of a cluster on the general 

 plan of the raceme are longer than the upper ones and make 



a somewhat flat-topped cluster, like 

 that of the hawthorn, the sheep 

 laurel, or the trumpet creeper. 

 This is called a corijmb. 



In many cases, for example the 

 parsnip, the sweet cicely, the gin- 

 seng and the cherry, a group of 

 pedicels of nearly equal length 

 spring from about the same point. 

 This produces a flower-cluster called 

 the umbel (Fig. 106). 



166. Sessile Floivers and Flower- 

 Chislers. — Often the pedicels are 

 wanting, or the flowers are sessile, 

 and then a modification of the 

 raceme is produced which is called a spU^e. like that of the 

 plantain (Fig. 107). The willow, alder, birch, poplar, and 

 many other common trees bear a short, flexible, rather scaly 

 spike (Fig. 108), which is called a catkin. 



The peduncle of a spike is often so much shortened as to 

 bring the flowers into a somewhat globular mass. This is 



Fie. 106.— Simple Umbel of Cherry. 



1 It is hardly necessary to say that the teacher will find it better in every way, if 

 material is abundant, to begin the study of flower-clusters with the examination of 

 typical specimens by the class. 



