80 



ARRANGEMENT OF FLOWERS ON THE STEM. [lESSON 11. 



207. The Spike, This is a flower-cluster with a more or les& 

 lengthened axis, along which the flowers are sessile or 

 nearly so; as in the Mullein and the Plantain (Fig. IGO), 

 It is just the same as a raceme, therefore, without any 

 pedicels to the flowers. 



208. The Head is a round or roundish cluster of flowers 

 which are sessile on a very short axis or receptacle, as in 

 the Button-ball, Button-bush (Fig. IGl), and Red Clover. 

 It is just what a spike would become if its axis were 

 shortened ; or an umbel, if its pedicels were all shortened 

 until the flowers became sessile or apparently so. The 

 head of the Button-bush (Fig. IGl) is naked ; but that of 

 the Thistle, of the Dandelion, the Cichory (Fig. 221), 

 and the like, is surrounded by empty bracts, which form 



W an involucre. Two particular forms of the spike and the 

 , head have received particular names, namely, the Spadix 



""' and the Catkin. 



209. A Spadix is nothing but a fleshy spike or head, with small 

 and often imperfect flowers, as in the Calla, the Indian Turnip 



(Fig. 1G2), Sweet Flag, &c. It is commonly covered by a peculiar 

 enveloping leaf, called a spatlic. 



FIO. IfiO. Spike of the common Plantain or Ribwort. 



FIG. 161. Head of the Butfon-lmsh (Ceplialanthiis). 



FIG. 162. Spadix and spaihe of the Indian Turnip ; the latter cut through below. 



