SECTION 8.] 



INFLORESCENCE. 



75 



winch arc sessile on a very short axis or receptacle, as in the Button-ball, 

 Buttou-busli (Fig. 205), and Red Clover. It is just wlial a spike would 



become if its axis were shortened ; or an 

 shortened until the flowers became sessile. 

 of the Button-bush is naked; but that of the Thistle, 

 of the Dandelion, and the like, is surrounded by empty 

 bracts, which form an Involucre. Two particular forms 

 of the spike and the head have received particular 

 names, namely, the Spadix and.the Catkin. 



212. A Spadix is a fleshy spike or head, with small 

 and often imperfect flowers, as in the Calla, Indian 

 Turnip, (Fig. 20G), Sweet Flag, etc. It is commonly 

 surrounded or embraced by a peculiar enveloping leaf, 

 called a Spatiik. 



213. A Catkin, or Ament, is the name given to the 

 scaly sort of spike of the Birch (Fig. 207) and Alder, 

 the Willow and Poplar, and one sort of flower-clusters 

 of the Oak, Hickory, and the like, — the so-called Amen- 

 taceous trees. 



214 Compound flower-clusters of these kinds are 

 not uncommon. When the stalks which in the sim- 

 ple umbel arc the pedicels of single flowers themselves 

 branch into an umbel, a Compound Umbel is formed. 



umbel, if its pedicels were all 



The head 



Fig. 20a. Head of the Button-bush (Cephalanthus). 



Fig. 206. Spadix and spatheof the Indian Turnip; the latter cut through below. 



Fio. 207. Catkin, or Ament, of Birch. 



