ON THE STRUCTURE OF CRUCIFEROUS FLOWERS. 3 
ever, whose inflorescence is corymbiform (Iberis umbellata, L.), have 
their two exterior petals enlarged like those of several Umbelliferæ. 
The same cause, that is to say, the compression proceeding from 
the axis, in both cases has effected this. It is likewise a remarkable 
fact, and not before noticed, that the foliole of the calyx which 
alternates with these two petals, and which is, therefore, itself 
likewise the furthest removed from the axis, is also constantly 
longer than the others. This may be easily seen in the flowers 
of Iberis umbellata, and T. pinnata. 
ANDRŒCEUM. 
The andrœæceum consists generally of six stamens, four long and 
two short (Zetradynamia). The long stamens are inserted side 
by side, and a little higher than the single ones. The stamens 
alternate exactly with the petals, but in this alternation, the twin 
stamens, if we may so term them, are so disposed, that each pur 
fills the space which one only of these organs ought to occupy.* 
The illustrious De Candolle at once perceived that the hexan- 
drous disposition of the androeceum was not contrary to the sym- 
metrical arrangement of the flower, since a stamen, or a pair of 
stamens was m opposed to each foliole of the calyx, and that 
consequently the andræceum and the corolla alternated in reality 
with each other. Unfortunately the plan which accompanies his 
Memoir is not rigorously exact.t Each of the double stamens is _ i 
opposed in part to a petal, and they are separated from each other. - 
This is, doubtless, an error of the artist, for the author says, posi- : 
e tively, page 19, and again, page 20, that these stamens are £rós- 
rapprochées. 
M. Lestiboudois, and M. Kunth 2 in their memoirs on the 
Cruciferæ, have given as their opinions, that instead of being 
geminate and simultaneously alternate with the petals, the longer | 
* This is well shown in the beautiful drawing ot Raphawes viida "eder = 
de chaque fam., Crucif. f. 1. 4: 
T Mém. sur les Crue, 1821, pl. I., fig. 6. 
_ € Obs. phytol. sur P inser. des étam. des Crucif. 1826, p. 6. 
T Zwei bot. Abhandl. HAE t x f.3. 
8 a: 
