INTRODUCTION TO BRITISH BOTANY xiii 



]ong stalks, while the upper are sessile, or nearly so, as in Wall- 

 flower, p. 28. 



In a cyme the stalks are irregularly branched, but the flowers 

 are nearly level, as in Elder, p. 135. 



The unihel 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. 131. 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, tiie secondary a partial. 

 This mode of inflorescence is common in the Umbelliferous Tribe, 

 p. no. 



A head resembles a simple umbel, except that the flowers are all 

 sessile, as in Scabious, p. 146. 



A catkin resembles a spike, except that the flowers are enclosed 

 each within a scale-like bract, as in Hazel, Plate 81. 



Other terms which are employed in the body of the work will be 

 explained as they occur, or in the description which precedes the 

 sumniary 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. 



It is not necessary to give an account of the Linneean system of 

 classification, nor of the various others which have been proposed. 

 Suffice it to say, the one generally adopted in Britain is a modifica- 

 tion of those of Jussieu and De CandoUe. Here the whole Vegetable 

 Kingdom is divided into three great Classjes. 



Class I. DICOTYLEDONS. 



In this Class are placed such plants as produce seeds divisible 

 into two lobes, or cotyledons. It is subdivided into four Sub-classes, 



TlIALAMIFLOR^, CALYCIFLOR^, COROLLIFLOE.E, and MONOCH- 

 LAMYDE.E. 



Sitb-class I. Thalamiflor.e. 



Flowers furnished with calyx and corolla ; petals distinct, in- 

 serted into the receptacle, or thalamus ; stamens springing from 

 the base of the ovary. 



Sub-class II. Calyciflor^. 



Flowers furnished with calyx and corolla ; sepals distinct, or 

 united ; petals distinct ; stamens inserted in the calyx, or close to 

 its base. 



Sub-class III. COROLLIFLOR.E. 



Flowers furnished with calyx and corolla ; petals united, bearing 

 the stamens. 



