THE STRUCTURE OF FLOWERS. 57 



should be compared with the usual form (Fig. 

 15, II.). 



Moreover, the liftji or posterior stamen is restored 

 in these flowers, being usuall}'' wanting in all such 

 irregular flow^ers, as of Labiates. 



Degradations. — As a sixth condition, it must be 

 observed that in a large number of plants some or 

 more of the floral whorls are wanting. 



In Strutli'iola and Protect, for example, there is no 

 corolla, only a calyx (white, green, or of some other 

 colour), stamens, and pistil. In others, even the calyx 

 is suppressed, as in Euphorbias, in which, indeed, one 

 stamen only represents a male flower. These degrada- 

 tions are regarded in most cases as indicative of their 

 having descended from plants w^hich possessed both 

 calyx and corolla ; but these whorls have been lost in 

 their evolutionary history. 



A few incomplete flowers are thought to be possible 

 descendants of primitive types, representing the earliest 

 stages, when Nature had not yet contrived to make 

 either a corolla or calyx. Such, <\(j., is the wax plant 

 {Myrica), of which there are eight species in South 

 Africa. Casuari'na, the " Beefwoods " of Australia, is 

 perhaps another ; and the willows and poplars of 

 England are descendants of some very early types ; but 

 the majority of incomplete flowers are undoubtedly 

 degradations from more complete flowers. 



Form. — In endeavouring to speculate as to how and 



