XIV 
instances they are doubled inwards at the edges, or induplicate; 
while in many they are twisted or contorted. 
The arrangement of the flowers upon the stem likewise requires 
notice. They are frequently situated singly at the apex of a stalk 
or peduncle rising from the root, or are solitary. In most plants, 
however, the stem is variously divided into small branches bearing 
the flowers. When a number of flowers are placed along a stalk 
without foot-stalks or pedicels, it is called a spike (Fig. 17). A 
drooping spike, containing stamens or pistils only, and dropping 
from the branch when withered, is termed an amentum or catkin. 
When the flowers of the spike are each supported by a foot-stalk, it 
becomes a raceme (Fig. 18). When the raceme is branched it is a 
panicle (Fig. 19). When the outer branches of the raceme or 
panicle are so elongated that the flowers are brought nearly to the 
same level with the inner ones, it is a corymb (Fig. 20). When the 
branches of the corymb terminate in a flower and then produce 
lateral stalks, as in the elder, it is styled a cyme (Fig. 21). When 
the flowers are arranged upon stalks branching from the apex of 
the stem, an umbel is formed, which, like the corymb, may be either 
simple or compound as the flowers stand singly upon the branches 
of the umbel or are supported upon secondary umbels rising from 
the extremities of the latter (Figs. 22 and 23). Sometimes the 
flowers are arranged in a close head or capitulum without pedicels, 
being situated upon a common disk or receptacle, as in the Dande¬ 
lion and other Composite. The flowers are in this case surrounded 
by a whorl of leaves like a calyx, to which the name of involucrum 
is given, a term applied to any whorl of leaves or bracts situated 
upon the flower-stalk. In the compound umbel there is usually a 
general involucrum beneath the primary umbel, while each second¬ 
ary umbel has one of its own, to which the term involucel is 
applied. 
All the parts of the flower must be regarded as modifications of 
the leaf. The sepals and petals arc nothing more than leaves some- 
