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 class 

 produced much confusion in our science ; for it is found that 

 plants having more than ten stamens, fre- 

 quently vary as to their numher j — 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 recejytacle. The manner 

 of insertion is always the same in the same 

 genus, and therefore there can be no con- 

 fusion 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 eiJcosi, 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 wliich tlie 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 difficult to 

 overtlirow the authority of custom. 



225. Order Monogynia^ one ;pistil. — ^AYe meet here with the 

 PricMy-Pear trihe^ in which the Cactus is the most important 

 genus. The natural family of which this is the type is called 

 Cactacece.^ 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 r/rnndijlorus), 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- 

 sissimua), with flowers hke crimson velvet, is still more superb than the grandiflo- 

 ■rus. The dififereut 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 numbers ? — 

 a. What name has been proposed as a substitute for Icosasdria? — 225. Cactus. — a. Diiferent species of 

 Cactus. 



