ANGIOSPERMS. 
6oi 
of each whorl is the same, and those belonging to the different whorls are placed one over 
another so as to form orthostichies, I adopt Payer's expression of superposed (instead 
of the ordinary one of * opposite'). When the stamens are superposed on the calyx or 
corolla, they are termed respectively antlsepalous and antipetalous ; if the members of a 
whorl fall between the median lines of those of the next whorl above or below, the 
whorls are alternate. When the number of members is the same in each whorl, they are 
said to be isomerous, when this is not the case heteromerous ; and Braun calls those flowers 
eucyclic in which the members of all the whorls are equal in number and alternate. It 
also happens however that members of the same kind arise subsequently between those 
of a whorl already formed ; as, for instance, five later stamens between the five earlier 
ones in Dictamnus Fraxinella (Fig. 414), and probably in many eucyclic flowers with ten 
stamens. Members subsequently introduced in this manner into a whorl may be called 
interposed. (For further details, •vide infra,) 
The consideration of the number of the parts of the flower cannot be separated from 
that of their relative position. But before entering more minutely upon this subject, the 
construction of the Floral Diagram must be described. 
The Floral Diagram is constructed diff'erently according to the purpose it is intended 
to serve. Some treat it as a somewhat free drawing of an actual transverse section of 
the flower, and indicate on it not merely the number and position, but approximately 
the form, size, aestivation, cohesion, &c. of its parts. This purpose is however clearly 
best attained by preparing as accurate drawings as possible of actual transverse sections 
of the flower-bud, which will then also contain much that would be superfluous for 
observations of a certain kind. But if it is merely required to represent the number and 
position of the parts of the flower in such a manner as to render as easy as possible the 
comparison in this respect of a number of flowers, it is best to disregard all other 
peculiarities, and to adopt one and the same plan for all diagrams, and that as simple as 
possible, so as to represent nothing but the variations in the relationships of number and 
position. This is the only purpose kept in view in the diagrams given in the remainder 
of this work, of which Figs. 406-408 may serve for the present as examples. They are 
constructed according to the rule already given on p. 188 ; the dot above the diagram 
always represents the position of the mother-axis of the flower; and the lower is there- 
fore the anterior part. Although mere dots would be sufficient to indicate perfectly the 
number and position of the parts of the ffower, diff'erent signs have nevertheless been 
rarely more, whorls is found in many Butomaceae and Alismacese ; usually when the number of the 
carpels is great they are arranged spirally. When the members of a series (calyx, corolla, etc.) are 
in one whorl, the series is said to be j7ionocyclic ; if in more than one, di-, tricyclic, etc. ; if in many, 
poly cyclic. 
In isostemonous flowers it frequently occurs that the stamens are antipetalous, as in Ampelideae, 
Rhamnacece, Plumbaginacese, Primulacese. This is usually ascribed to the abortion of an exterior 
whorl of antisepalous stamens, an assumption which is based either on the presence of a whorl of 
staminodes in the place of the missing stamens, or on the presence of two whorls of stamens in 
allied Orders. 
It not unfrequently happens in a diplostemonous flower that the stamens of the outer whorl are 
antipetalous {Limtianthes, Rutn, Diciammis (Fig. 4I4), Pyrola, Monotropa, Chry&osplenium, Epilohium, 
CEnothera, Fuchsia, Geraniacese, Zygophyllacere, Crassulacese, Ericacese, Rhodoraceae, etc.) : when 
this is the case the androecium is said to be ohdiplostemotious ; the carpels are superposed on the 
stamens of the outer whorl, and therefore also on the petals. The most satisfactory explanation of 
obdiplostemony is that given by Celakovsky (Flora, 1875), though, as we shall see below (note, p. 
606), it cannot be apphed in all cases : according to him the staminal whorls arise in regular acropetal 
succession, the antisepalous stamens being developed first, as in direct diplostemony; the antipetalous 
stamens are developed internally to the others but become gradually displaced outwards, so that they 
appear either to lie in the same whorl as the antisepalous stamens or externally to them. This is the 
real meaning of the 'interposition' mentioned above. (For further details on these points see Gray's 
Structural Botany, and Eichler's BlUthendiagramme.)] 
