250 Dr Dickson on Diplostemonous Floiuers, (&c. 



In the Aurantiacese, we have, in staminal groups, 



of which Payer has fully detailed the development. These 

 groups alternate with the petals. In each group, the suc- 

 cessive evolution of the stamens extends, in single line, later- 

 ally to right and left from a central oldest stamen super- 

 posed to a sepal ; those stamens, therefore, being youngest, 

 which are furthest removed from the central stamen or 

 terminal lobe of the compound stamen.* Payer, moreover, 

 describes the arrangement in Tijjlimsia trifoliata^ in the 

 same family, as diplostemonous with the carpels superposed 

 to the petals. The fact of the carpels here being super- 

 posed to the petals is important, as such an arrangement 

 cannot fail to recall that in Geranium, Erica, &c., and of 

 course suggests that the diplostemony in Tiplirasia, and 

 many other Aurantiacese, is of the same spurious character 

 as in these plants. Now, if this is the case, does not the 

 androecium of Citrus bear to that of Tiplirasia, a relation 

 exactly analogous to that which the whorl of apparent leaves 

 of Galium aparine, consisting of opposite leaves, wdth a plu- 

 rality of intervening lobes, does to that of G. cruciatum, 

 where the intervening lobes are reduced to one on either 

 side of the axis ? 



Again, in the Philadelphaceee, there are, in Fliilodelphus, 

 staminal groups, the development of which, as described by 

 Payer, is strikingly like that in Citrus ; while we have an 

 apparent diplostemonous form occurring in Deutzia, But 

 we seem further to have a form intermediate between 

 PhilacMphus and Deutzia, in Decumaria, which is described 

 as having thrice as many stamens as petals, there being 

 single stamens superposed to the sepals, and pairs of stamens 

 superposed to the petals. f Thus, in the Philadelphaceae, 

 we have — 1st, in Philadelplius, compound stamens with 

 indefinite lobes ; 2d, in Decumaria, a reduction in the num- 

 ber of the staminal lobes, resulting in a condition apparently 

 analogous to that in Monsonia ; and 3d, in Deutzia, an 

 apparent diplostemony, probably analogous to that in 

 Geraniura, &c4 



* Payer, Organogenie, p. 114, pi, 25, t Endlicher, Genera, p. 1187. 



;|: Visnea, in tlie Ternstrremiacese, is probably another example of a reduced 

 pulyadelplioua form. In V. mocanera, Payer has shown that, of its 15 stamens, 



