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PLANT BIOLOGY 



open first. Another special form of spike is the catkin, 

 which usually has scaly bracts, the whole cluster being 

 deciduous after flowering or fruiting, and the flowers (in 

 typical cases) having only stamens or pistils. Examples 



are the "pussies" of willows (Fig. 



182) and flower-clusters of oak (Fig. 



180), walnuts (Fig. 204), poplars. 



Fig. 216. — Head of Clo- 

 ver Blossoms. 



Fig. 217. — Corymb of Candy- 

 tuft. 



When a loose, elongated centripetal flower-cluster has 

 some primary branches simple, and others irregularly 

 branched, it is called a panicle. It is a branching raceme. 

 Because of the earlier growth of the lower branches, the 

 panicle is usually broadest at the base or conical in outline. 

 True panicles are not very common. 



When an indeterminate flower-cluster is short, so that 



