264 THE FLOWER. 



472. The petals, however, are frequently absent ; when the 

 flower is said to be apetalous, as in the Anemone (Fig. 325), Clem- 

 atis, Caltha, &c., in the Crowfoot 

 Family, other genera of which are 

 furnished with both calyx and corol- 

 la ; as in some species of Buckthorn, 

 while others bear petals ; as in our 

 Northern Prickly Ash* (Ord. Zan- 

 thoxylace^), while the petals are 

 present in the Southern species. 

 They are constantly wanting in a 

 large number of families of Exoge- 

 nous plants, which on this account 



form the division Apetalce. When the calyx is present while the 

 corolla is wanting, the flower is said to be monochlamydeous, that 

 is with a perianth (417) or floral envelope of only one kind ; as in 

 the cases above mentioned. But sometimes both the calyx and 

 the corolla are entirely wanting, as in the Lizard's-tail (Ord. Sau- 

 ruraceas) when the flowers, being destitute of floral envelopes, are 

 termed achlamydeous. The essential organs (418) are neverthe- 

 less present in these cases, so that the flower is perfect (or bisex- 

 ual) , although incomplete. 



473. A still further reduction, however, occurs in many plants ; 

 where even these essential organs are not both present in the same 

 flower, but the stamens disappear in some flowers, and the pistils 

 in others. Such flowers are said to be diclinous, unisexual, or sep- 

 arated ; that which bears stamens only is termed sterile, or stami- 

 nate, and that provided with pistils only, fertile, or pistillate. This 

 separation of the essential organs is very frequently met with 

 where one or both of the floral envelopes are present, as in Me- 

 nispermum (Ord. Menispermacese) and Prickly Ash (Ord. Zan- 

 thoxylacese) ; but when these are absent, it presents instances of 

 the greatest possible reduction of which the flower is suscepti- 



* In our Northern Zanthoxylum the monochlamydeous perianth which is 

 present may, however, be justly held to be the corolla, and not the calyx, be- 

 cause the five stamens alternate with it, just as they do with the undoubted 

 petals of Z. Carolinianum : in this case, therefore, we may say that the calyx 

 and not the corolla is suppressed. See Gen. Illustr., 2, p. 148, tab. 156. 



FIG. 325. Flower of Anemone Pennsylvanica (apetalous or monochlamydeous). 



