INTRODUCTION 15 
amongst Sedges, etc. When the spike is pendulous 
it is a catkin, as in the pedunculate Oak. 
When the stalks of the lateral branches of an 
inflorescence attain the same length as that of the 
axis or rachis the inflorescence is called a corymb, 
when all the flowers are at the same level. An umbel 
is a corymb with the main axis reduced to a point 
from which the branches radiate from a common 
centre. A familiar example is the poisonous Hemlock. 
The umbel may be simple, or partial, in which last 
case the ray bears an umbellule. 
When the flowers of the umbel are sessile we 
have the head or capitulum in Composite, the stalk 
being enlarged to form a receptacle upon which they 
are borne. The Hawkweeds are examples of this. 
The former type of inflorescence is monopodial, 
the growing point being continuous each year in the 
same direction, the branches regularly succeeding, 
but not overtopping the main stem, as in the Scotch 
Pine. 
In the sympodial inflorescence the lateral shoots 
in succession overtop the main axis, and the growing 
point is thus modified by the shooting out of the 
side branches which assume that position, in position 
if not in origin. 
The rhipidium of the Iris is an example of this type 
of inflorescence. The cyme is made up of a number 
of flowers which form a straight sympodium ; when 
one branch bears upon its successor one only the 
cyme is monochasial, if two a dichasial, etc. 
