548 
PHANEROGAMS, 
which spring from the upper margin of the hollowed-out receptacle which constitutes 
the inferior ovary \ 
The size and form of the stamens frequently varies within one and the same 
flower; thus, for instance, in the Cruciferse there are two shorter and four longer 
(tetradynamous), in the Labiatse two larger and two shorter (didynamous) stamens ; 
in Cen/radem'a, as was shown in Fig. ^64, A, B, they are not only of different size, 
but are also differently segmented. A correct conception of the history of develop- 
ment and a comparison of the relationships of number and position in nearly allied 
plants enable one to apply the term stamen even to structures which have no anther 
and therefore want the ordinary physiological character of stamens. Thus, for 
example, in Geranium there are two whorls of fertile stamens, while in the nearly 
related genus Erodium those of one whorl are without anthers. Such sterile stamens 
or Staminodes generally undergo further metamorphosis, by which they become unlike 
the fertile ones and not unfrequently petaloid, as the innermost staminal leaves of 
Aquilegia ; or assume very peculiar forms, as in Cypripedium (Fig. 372, s). In 
Fig. 372.— Flower of Cypripeduan Calceoltcs after removal of the perianth. 
some Gesneraceae a glandular structure or nectary is found in place of the poste- 
rior stamen (compare the drawing of Columnea, Fig. 416). Metamorphoses of 
this kind may be considered as the first steps to a condition of abortion, the final 
stage of which is the production of a vacancy at the spot where the stamen should 
be, as in the Labiatae, an order closely allied to the Gesneraceae, where, in the place 
of this staminode there is no structure whatever ; instead of the five stamens to which 
the plan of construction of the flower points, there are only four, even the rudiment 
of the fifth, the posterior one, being suppressed, as is seen in Fig. 373 ^. Phenomena 
of this kind altogether justify the hypothesis of abortion in those cases in which 
the absent organ does not disappear in the course of development, but never comes 
. ^ Compare the account of the development and significance of the flowers of Orchidese in the 
sequel. 
2 [Peyritsch however (Sitzungsb. der k. Akad. der Wissen, zu Wien, 1872) infers, from the 
constant reversion to fours in the peloric flowers of Labiatce, and from other considerations, that the 
original type of the flower is tetramerous.] 
