160 
CLASS ICOSANDRIA. 
twelve, and andria., stamen ; this was not, as might be inferred 
from the name, confined to twelve stamens, but contained from 
ten to twenty, without any regard to their insertion. This chiss 
produced much confusion in our science ; for it is found that 
plants having more than ten stamens, fre- 
quently vary as to their member; — there 
being no difficulty in distributing all plants 
of this class in the two next classes, the 
plants which it contained are arranged 
under Icosandria, if the stamens are on the 
calyx^ and Polyandria, if the stamens are 
inserted upon the receptacle. The manner 
of insertion is always the same in the same 
^enus, and therefore there can be no con- 
tusion with respect to determining the 
classes upon this principle. 
This omission of one class changes the numbers of the re 
maining classes ; as Icosandria, which was formerly the twelfth, 
is now the eleventh class ; and so on with the other classes. 
On account of these changes, it is better to learn the classes 
by their appropriate names, as Monandria, Diandria. More- 
over, the name of each class conveys an idea of its character. 
a. The name Icosandria, from eikosi, twenty, and andria, stamens, seems not, 
however, exactly well chosen to represent the eleventh class, which is not confined 
to twenty stamens, having sometimes as few as ten, and in some cases nearly a 
hundred stamens. Darlington proposed to call the class Calycandria, from calyx 
and andria, as the insertion of the stamens on the calyx is the essential circum- 
stance on which the class depends ; but though this change has been approved, the 
former name is still used. Thus, with respect to the name of the great American 
continent, all allow it should be Columbia, after its discoverer ; but it is difiicult to 
overthrow the authority of custom. 
225. Order Monogynia^ one pistil. — ^We meet here with the 
Prichly-Pear tribe., in which the Cactus is the most important 
genus. The natural family of which this is the type is called 
CactaceoB^ or the Indian-fig tribe. The sepals are numerous and 
confounded with the petals adherent to the ovary. Stamens 
indefinite, cohering more or less with the petals and sepals. 
These plants are succulent shrubs, with angular or flattened 
stems ; they are remarkable for their development of cellular 
tissue with spiral cells. 
a. Among the most splendid of the Cactus species is the night-blooming Cereus 
(Cactus graiidijiorus), having flowers nearly a foot in diameter, with the calyx yel- 
low, and the petals white. The blossoms begin to expand soon after the setting of 
the sun, and close before its rising, never again to open. Another species (specios- 
sissi?nus), with flowers like crimson velvet, is still more superb than the grandiflo- 
rus. The dilferent species of this genus are distinguished by a diversity of common 
Why is it important to learn the appropriate names of the classes, rather than their nunbersi — 
a. What name has been proposed ns a substitute for Icosandria 1 — 225. t^actus. — a. Ditferent species of 
Oacius. 
