28 



FLOWERS 



elongated stem bearing normally developed leaves in the axils 

 of which the flowers occur. Thus, if a Pumpkin or Gourd vine 

 should remain short, the flowers instead of being well separated 

 as they normally are, would be crowded, and, with the reduction 

 of leaves to bracts, a typical flower cluster would result. Most 

 small flowers are produced in clusters. For small flowers polli- 

 nated by insects, there is considerable advantage in the cluster 



habit, since the cluster, being much 

 more conspicuous than the individual 

 flowers, serves well as an attractive 

 device. 



Flower clusters are divided into 

 two main classes according to their 

 method of development. In the 

 corymbose or indeterminate cluster, 

 growth at the tip and the develop- 

 ment of new flowers just behind 

 continues throughout a considerable 

 period, thus producing a cluster in 

 which the older flowers are left 

 farther and farther behind. As the 

 term indeterminate suggests, such a 

 method of development permits a 

 rather indefinite expansion of the 

 cluster. In the cymose or determi- 

 nate cluster, the oldest flower is 

 formed at the tip, which is thereby 

 closed to further growth, and the 

 new flowers are formed from buds 

 developing lower down. Such a 

 cluster is much limited in its power 

 to expand. The flower clusters of Apples and Pears, known as 

 cymes, illustrate the determinate type of cluster. 



The simplest form of the indeterminate cluster is the raceme, 

 an unbranched cluster in which the flowers are borne on short 

 stalks. The racemes of the Shepherd's-purse, Radish, Cabbage, 

 and others of the Mustard family, in which the flower cluster 

 may continue its expansion for a long period, producing new 

 flowers at the tip while pods are maturing at the base, well 

 illustrate the nature of the raceme. (Fig. 29.} The racemes of 



FIG. 29. Raceme of Com- 

 mon Cabbage (Brassica). From 

 Warming. 



