48 | ELEMENTARY BOTANY 
but many plants have compound umbels, that is to say, the — 
inflorescence consists of a number of simple umbels, each with 
its own involucre, and the whole inflorescence with a common 
involucre. These involucres may be wanting. This inflores- 
cence gives its-name to the order Umbellifere (Plate IL, 
Fig. 50). : 
In the capitulum or head the flowers are sessile, not stalked. 
The apex of the main stem generally becomes dilated into 
a flattened receptacle, each flower in its bract, the whole 
receptacle being protected by an involucre of bracts. This is 
well seen in the Composite. (See Fig. 118.) The receptacle 
here should not be confused with the flower stalk on which 
the floral leaves are situated. 
cymose. The growth of the main stem is invariably 
inflorescences. arrested in plants which have cymose inflores- 
cences. Sometimes only one flower is borne by the stem, 
and the inflorescence is then said to be solitary ; but as a rule 
growth is continued by 
means of lateral branches. 
In some cymes, branches 
are developed only on one 
side of the main axis, as in 
the comfrey and forget-me- 
not, the opposite branch 
being undeveloped in each 
case. (Plate IL, Fig. 52.) - 
Sometimes the vigorous 
branches develop _ alter- 
nately, first on one side, 
then on the other. 
In some inflorescences 
the cymes are two - sided. 
Fic. 53.—INFLORESCENCE OF Thus in the stitchwort the 
ce Ne main stem ends in a ‘lower. 
A 2-branched cyme. ae 
This is the first flower to 
be formed. Underneath this two branches arise opposite 
each other, each terminating in a flower, beneath which two 

