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A flower, in its most perfect form, consists of an outer envelope 
composed of several leaf-like divisions called the calyx, an inner series 
of similar leaves called the corolla, and a number of small bodies 
situated within these denominated stamens and pistils. The usual 
arrangement of these parts may be seen in Fig. 5. The outer 
series of leaves, forming the calyx, are termed sepals; they are 
usually green. The leaves of the inner series, or corolla, are called 
petals, and, being generally highly coloured, form the most con- 
spicuous part of the flower; in our figure they are of the same 
number as the sepals and alternate with them, but in many flowers 
several series of petals are developed. ‘The calyx is sometimes 
coloured like the corolla, and can then only be distinguished from 
the latter by its position, as in Lilies and most other endogenous 
flowers ; the floral leaves are then collectively styled a perianth. 
Where only one series of floral leaves is present, it is considered as 
a calyx, whether coloured or not. Sometimes the calyx is deciduous, 
that is, it falls off before the flower opens, as in the Poppy tribe, 
aad in some plants both calyx and corolla are wanting. The 
sepals are occasionally united at their base into a tube, and the 
same is frequently the case with the petals, as in the Foxglove, 
Primrose, and many other flowers. The calyx is frequently re- 
duced to a mere rim, as in some of the Umbelliferze ; while in the 
Compositze, the order to which the Dandelion and Thistle belong, it 
is represented only by a circle of hairs or scales beneath the corolla, 
and is then denominated a pappus. In the Grasses there 1s no regular 
calyx or corolla, these envelopes being represented by two series of 
scale-like bracts, the outer of which are called g/wmes, the inner 
palee. Sometimes, as in the Calla and the wild Arum of our 
hedges, the floral organs are enclosed in one large bract, which 
receives the name of a spathe. 
The petals are usually equal in number to the sepals, or some 
multiple of that number, and such flowers are called by botanists 
symmetrical ; when the contrary is the case the flower is said to 
