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 antisepalous 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 m Dictamnus Frax'inella (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 differently 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 flower, different signs have nevertheless been 



rarely more, whorls is found in many Butomaceoe 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 monocyclic ; if in more than one, di-, tricyclic, etc. ; if in many, 

 polycyclic. 



In isostemonous flowers it frequently occurs that the stamens are antipetalous, as in Ampelidese, 

 RhamnacejE, Plumbaginacese, Primulaceae. 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 {Limnanthes, Ruta, Dictamnus (Fig, 414), Pyrola, Monotropa, Chrysosplenium, Epilobium, 

 CEnothera, Fuchsia, Geraniacese, Zygophyllacege, Crassulaceoe, Ericaceae, Rhodoracese, etc.) : when 

 this is the case the androecium is said to be obdiplostemonous ; 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 applied 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.)] 



