522 [Perigynous Exooens. 



Sub-Class III. PERIGYNOUS EXOGENS. 



The first group in this Sub-class is so evidently allied to the Chenopodal 

 Alliance, that the genera are in many cases referred to the one or the other 

 according to the varying views of systematists, and Basellads are really 

 almost always considered as a perigynous form of Chenopods, which, more- 

 over, are in certain cases, as for example in Beet, truly perigynous. This 

 seems to show that Chenopodal s on the one hand, and Ficoidals on the 

 other, form the boundary between the Hypogynous and Perigynous series. 



It is evident that in the Alliances which are thus collected, there is a 

 constant and powerful tendency to the cohesion of the floral organs, for half 

 of them consists of Orders having monopetalous flowers, a structm-e which is 

 rare in the hypogynous Sub-class, and if it is seen there, is seldom accom- 

 panied by any union of the stamens to the petals, such an occurrence, when 

 it is observable, as in Epacrids, being altogether exceptional. Here, on the 

 contrary, the monopetalous coroUa is habitually associated with epipetalous 

 stamens. The tendency to adhesion is not indeed confined to the separate 

 parts of the same ring of organs, or to the stamens with the calyx or corolla, 

 but also not unfrequently occurs between the ovary and the parts which 

 grow around it ; the consequence of which is, that we find a partly inferior 

 ovary in nearly every one of the Alliances of the Perigynous Sub-class. 

 But although this is a manifest approach to the condition of the Epigynous 

 Class, yet it is seldom the cause of any confusion, because the combina- 

 tion of the calyx, coroUa, and stamens with each other is only partial, and 

 is rarely accompanied by a similar cohesion of the carpels, whose styles 

 remain separate even when their ovaries are consolidated. This is obvious 

 among Appleworts and Hydrangeads, two quasi-epigynous foims of the 

 Ranal and Saxifragal AUiances. 



