4 
Principles of Classification . 
Calyx . — Several varieties of calyx are described ; 
it is called perianthium, or perianth, when it includes, 
the other parts of the flower, as in the primrose and 
the pink, but it is sometimes wanting, as in the tulip ; 
in some cases it remains till the fruit is ripe, and in 
others it drops off before the flower is expanded *, in 
mallow it is double, and in scabious it is triple. The 
involucrum is a kind of calyx peculiar to umbelliferous 
plants, as hemlock or parsley ; and it is either partial 
or general, as it includes the whole or only a part of 
the umbel. The amentum or catkin is a common re- 
ceptacle, furnished with scales, each of which includes 
the parts of fructification, and the whole forms an ag- 
gregate flower. The willow and the fir tribes furnish 
examples of tfee catkin. The spatha , or sheath, is a 
kind of calyx which appears in the snowdrop and nar- 
cissus. The gluma or glume is the calyx peculiar to 
grasses, and it is of a chaffy texture. 
Corolla. — -The corolla is included within the calyx, 
and usually exhibits those rich and beautiful colours 
which are so much admired in plants. When the co- 
rolla is composed of different parts, they are called, 
petals ; it consists sometimes of one petal, and then it 
is said to be monopetalous, as in the primrose ; and 
when it consists of many petals, it is called polypeta- 
Ions, as in the rose. 
A monopetalous corolla is divided into two parts $ 
the tube, or cylindrical part, included in the calyx, 
and the limb, limbus, which is spread out, as in the 
primrose. When the corolla consists of many petals, 
as in the pink, that part of it which appears without 
the calyx is called the border or lamina , and that part 
inclosed in the calyx is denominated unguis , or claw. 
