90 



THE FIRST BOOK OF BOTANY. 



EXERCISE XXXIV. 

 Varieties of Inflorescence. 



FIG. Ifil. 



SIMPLE. 

 Fio. 162. 



FIG. 163. 



Head. 



Spike. 



Spadix. 



HEAD. A more or less globular cluster of flowers, 

 sessile upon the receptacle. 



SPIKE. A cluster of flowers, sessile upon a rachis. 



SPA'DEX. A spike with a thick rachis, and covered 

 around by a single large leaf, or bract, called a 

 spathe. 



stem, and so, as the rachis may grow on, sending off flowers 

 from its side, we say the inflorescence is indefinite. 



The primary, or main stem, of a plant sometimes ends defi- 

 nitely, or with a flower, while the branches, or secondary stems, 

 grow on, or are indefinite. Sometimes the main stem is indefi- 

 nite, and the branches are definite. When both kinds of in- 

 florescence are found upon the same plant, it should be stated. 



To determine whether a flower-head is definite or indefinite, 

 observe whether the unopened flowers are at the top or on the 

 lower part of the cluster. It is only in rare instances that 

 they all open so nearly at the same time as to show no differ- 



