STRUCTURE OF FLOWERS. 109 



of the calyx, corolla, or perigone, so disposed that there 

 are two exterior, one or two entirely interior, and one 

 or two intermediate, that is to say, half covered by one 

 side of one of the outer ones, and overlapping by the 

 other margin one of the inner ones ; this is very evident 

 in the calyx of the Rose, and I have called it Quin- 

 cunxial ^Estivation (PI. 19, figs. 10, 12). 



The flowers of the Papilionaceae present one of their 

 petals more exterior, and embracing all the others, two 

 intermediate ones face to face, and two inner ones also 

 face to face ; this constitutes Vexillary Estivation, 

 (PI. 19, fig. 8.) 



The variety of these irregular aestivations is very 

 great, being connected with the irregularity of the 

 flowers ; and in a great number of cases it may seem as 

 a sign whereby to discern flowers perfectly regular, or 

 more or less irregular. We may see different examples 

 in PI. 19, figs. 7, 9, &c. 



Before quitting this subject, I ought also to remark, 

 that the aestivation of the parts of the calyx and 

 corolla have not any necessary affinity, even in the more 

 regular families : thus, the aestivation of the Malvaceae 

 (PI. 19. figs. 2, 7) is valvate in the calyx, twisted in the 

 corolla; that of the Linaceae and Cistineae (PI. 19, fig. 5) 

 is twisted in both organs, but the torsion of the corolla 

 is in a different direction from that of the calyx. This 

 fact, with a multitude of others, tends to prove, that it 

 is contrary to the nature of things to consider the calyx 

 and corolla as two rows of one organ which is called 

 perianth ; but that they are, in reality, organs as 

 different as all those of which the flowers are composed. 

 There are perigones of which the parts are in two rows, 

 and each row has a particular aestivation ; such is the 

 flower of Tradescantia Virginica (PI. 19, fig. 3), where 

 the outer row is foliaceous and valvate, and the inner 



