04 THE FLOWERING PLANT. 
long and two short (didynamous). It will be remembered that 
in this flower the odd petal is anterior, and there should, there- 
fore, be an odd posterior stamen, since the outer whorl of stamens, 
which alternate with the petals, is retained. This, however, is 
almost always absent. Very rarely, however, a minute stamen 
is found in this position. Snapdragon is a similar case. Take 
one of its flowers, and carefully split open the gamopetalous 
corolla along one side. Upon spreading it out, you will find in 
its posterior side (7.e., next the stem and opposite the rounded 
swelling at the base of the corolla tube), near its attachment to 
the receptacle, a minute white projection, the vestige or rudiment 
of the lost fifth stamen. The foxglove, a near ally, possesses 
four stamens and no rudiment, while pentastemon, a common 
garden flower related to this, possesses a very large fifth stamen, 
devoid, however, of an anther, which curves down to the lower 
side of the flower. Finally, mullein, also a relative, has five 
perfect stamens. The speedwell, which belongs to the same 
group of flowers, presents still further reduction. The sepals 
and petals are four, but the stamens only two. In most orchids 
there is only one perfect stamen, the anterior one of the outer 
whorl. One orchis, however, ladies’-slipper (Cypripedium), has 
two stamens, belonging in this case to the inner whorl. These 
facts, and the presence of more or less complete rudiments of 
other stamens (cf. p. 88), lead to the conclusion that the one- 
stamened orchis is descended from forms which possessed six 
perfect stamens, arranged in two alternating three-membered 
whorls, as, for example, in snowdrop and lily (fig. 38). Stamens 
are absent altogether in female or pistillate flowers, and this often’ 
appears to be the result of reduction. Some of the flowers on 
certain plants are neuter, 2.e., devoid altogether of sporophylls, 
and reduction has undoubtedly taken place in such cases. 
Stamens are sometimes increased in number in cyclic flowers, 
instead of being reduced. In the wallflower, for mstance, there 
are four sepals and four petals, but six stamens—four long and 
two short (tetradynamous). The petals are obliquely placed, 
while the short stamens are /ateral in position, and the long ones 
are grouped in two pairs, one anterior and the other posterior. 
Each pair appears to have arisen by the splitting of a single 
stamen. This is supported by the fact that in some tetradynamous 
flowers a partly-split stamen is occasionally found instead of a 
pair. Branching may also occur. In St. John’s wort there are 
three or five groups of stamens, each group of which has been 
formed by the branching of a single stamen at an early stage of 
development. Mallows and hollyhocks, again, possess numerous 
stamens formed by the branching of five originalones. The terms 
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