XIV INTRODUCTION. 



flowers on long stalks, while the upper are sessile, or 

 nearly so, as in Stock, p. 67. 



In a cyme the stalks are irregularly branched, but the 

 flowers are nearly level, as in Elder, p. 297. 



The umbel is a mode of inflorescence in which the 

 flower-stalks spring from a common centre, and bear 

 each a single flower, as in Ivy, p. 287. When the stalks 

 bear, instead of a single flower, a second umbel, the 

 inflorescence is a compound umbel, the primary division 

 being termed a general umbel, the secondary a partial. 

 This mode of inflorescence is common in the Umbel- 

 liferous Tribe, p. 246. 



A head resembles a simple umbel, except that the 

 flowers are all sessile, as in Scabious, p. 318. 



A catkin rasembles a spike, except that the flowers 

 are enclosed each within a scale-like bract, as in Hazel 

 p. 573. 



Other terms which are employed in the body of the 

 work will be explained as they occur, or in the descrip- 

 tion which precedes the summary of each Natural 

 Order. A glossary will also be found at the end of the 

 volume, containing definitions of most of the common 

 terms in use. 



