74 
PLANT MORPHOLOGY. 
In many flowers there is an additional part which is 
usually green and leaf-like, as in Cannabis Indica, 
known as the calyx, the individual parts being known 
as the sepals. 
A great many flowers produce, in addition to calyx, 
stamens and pistils, another circle of parts which, as a 
rule, are quite bright and attractive, as in the rose, 
geranium, violet, etc. This circle of parts is situated 
between the calyx and the stamens and is called the 
corolla, the individual parts being termed petals. 
The calyx and corolla are regarded as the non-essen- 
tial parts of the flower and together constitute the 
perianth or perigone. 
A complete flower is said to be symmetrical when the 
number of parts in each circle is the same or a multi- 
ple of it; as a rule the number of stamens is some 
multiple of one of the other parts, as in geranium, 
where we find five sepals, five petals, ten stamens and 
five pistils. 
Flowers are also spoken of as regular or irregular, 
according to whether all the parts of a circle are uni- 
form in shape or not; the flowers of geranium are regu- 
lar while those of violets are irregular. 
Pistillate and staminate flowers may be borne upon 
the same plant, as in white-oak or castor-bean, when 
the flowers are said to be monoecious ; or they may be 
borne upon separate plants, as in willows and poplars, 
when they are said to he dioecious. 
( b ) COMPOUND FLOWERS. 
The flowers of the Compositse are borne on an en- 
larged receptacle, which is subtended by one or more 
circles of bracts, these constituting an involucre. The 
flowers are of two kinds, and they receive different 
names because of their form and position. Those situ- 
