DICOTYLEDONS. 
^45 
number of stamens in the interposed and outer whorl is doubled. The order 
TEsculineae is of special interest in this connection, since in some of its families 
(Acerineae and Hippocastanese, Fig. 455) the interposed staminal whorl remains 
incomplete, so that the total number of stamens is not a multiple of the typical 
fundamental number (five). Among pentamerous flowers Lythrarieae, Crassulaceae, 
and Papilionaceae may be mentioned in addition, and among tetramerous ones 
CEnothereae, in which a complete staminal whorl is interposed. 
One of the most remarkable deviations from the ordinary structure takes the 
form in not a few families of Dicotyledons of the simple staminal whorl being 
superposed on the corolline whorl, as shown in Figs. 456, 457, and as occurs also 
in the Rhamnacese, Celastrinese, the pentandrous Hypericinese, and Tilia. Pfeffer ^ 
has shown that the two superposed whorls of Ampelidese arise independently of one 
another and in acropetal order, while on the other hand in Primulaceae they first 
appear in the form of five projections each of which forms a stamen, and from each 
of which a petal subsequently grows outwards. In these cases we have no sufficient 
ground for the hypothesis that an alternating whorl has been suppressed between 
the two superposed ones ; although in other cases this supposition is justified, or at 
least is very probable. Thus in the order Caryophyllineae, families, genera and 
Fig. 458.— Diagram oi Scleranthus FIG. 459. Diagram of Phytolacca FIG. 460.— Diagram oi Celosia 
(Paronychiacere). (Phytolaccacete). (Aniaranthaceae). 
species occur in which the corolla is absent and the stamens are superposed on the 
sepals ; and since in the same natural group species also occur with a corolla, it may 
be assumed that where the corolla is absent this is the result of abortion. The 
diagram of these plants (Figs. 458, 459) is compHcated still further by the tendency 
which they exhibit to a de'doublement of the stamens and even of the carpels. 
When a flower has more stamens than sepals or petals, this may be the result, 
as has already been mentioned, on the one hand of an increase in the number of 
staminal whorls (as in Fig. 451), or on the other hand, of the interposition of 
a perfect or imperfect whorl among the typical ones, or of de'doublement of the 
stamens (as in Fig. 458). These cases must be clearly distinguished from those in 
which a larger number of stamens results from the branching of the original ones, 
a phenomenon which is found in different sections of Dicotyledons, and is some- 
times constant in whole families (see p. 544). Thus, for instance, in Dilleniacese 
(Fig. 461), Aurantiaceae (Fig. 462), and Tiliaceae (Fig. 463), each symbol which 
indicates a group of anthers corresponds to a single original stamen. In this case 
the number of original stamens is the same as that of the petals and sepals; 
' Pfeffer, Bot. Zeitg. 1870, p 143; and Jahrb. für wissensch. Bot. vol. YIII. p, 194: (see 
supra, p. 609). 
