178 



symmetry. The said phenomeuoii is to be seem in Carina in 

 botli whorls of the perianth. The consequence is that the en- 

 closed part is less developed as compared with the flanking 

 ones. If, moreover, the enclosed parts of the subsequent whorls 

 are on the same side of the flower, this must necessarily entail 

 symmetrical structure of the whole. When again drawing 

 attention to figures 7 — 12 it must strike us that on the left 

 side, where p^ and a (= enclosed petal and inner ala) spring, 

 the flower is poorly developed: the basal portion of a being 

 much inferior to labellum and ,i% p^ narrower than /;' and ^r\ 

 the distance between the rudimentary styles s and .s-' very 

 small and one of the outer alae liable to suppression. In contrast 

 with it we find on the right side a well grown ala /? which 

 in the „alatae" is never wanting, a broad winged style flanked 

 by two inner staminodes of considerable range. Although the 

 symmetry be not absolutely complete owing to the stamen 

 which has developed on one side only, it is so striking that 

 everybody will place the dividing plane between S and the 

 middle of s s' (fig. 18). 



It is the alae which disturb the symmetry in the periphery 

 of the flower. Whilst the brickred Canna, the starting-point 

 of the present examination, is as a rule in possession of three 

 outer alae, one of these may every now and then remain un- 

 developed or at least reduced to a small appendage of a. But 

 in other species it is altogether absent and so may be / and 

 ft. Also a may be suppressed. Systematists have founded on 

 these differences their division in trialatae, hialatae together 

 making up the subgenus Eiicanna, and the subgenus Distemon '), 

 which lacks not only ft and y, but even a and possesses merely 

 X and labellum. Notwithstanding the structure of Distemon is 

 the simplest we cannot but admit that it has gone through 

 the longest series of development since the period in which the 

 prae-Canna showed an insect-attracting perianth, six ordinary 



1) Distemon seems, at least in temperate regions, altogether to have disappeared 

 from cultivation. 



