Dr Dickson on Diplostemonom Flowers^ (&c. 253 



It has been suggested to me, that if we were to admit 

 the occurrence of accessory stamens, there would be no 

 reason why these might not sometimes be placed on the 

 same circle with, or even internal to, the primary ones, just 

 as stipulary lobes may appear on the same level with the 

 base of a leaf, or, as in the so-called axillary stipule, above 

 it or on its inner face. I have already, when treating of 

 Tiiplirasia and Deutzia^ admitted the possibility of accessory 

 stamens being on the same circle with the primary ones. As 

 to accessory stamens being internal to the primary ones, I 

 think it not at all improbable that such an arrangement 

 may also occur ; and, in compound stamens, an analogous 

 phenomenon would be found in the Myrtacese, where the 

 staminal lobes appear in centripetal succession as regards 

 the axis.* Now, the possibility of accessory stamens being 

 internal to the primary ones, may be supposed by some to 

 invalidate the morphological distinction of diplostemonous 

 flowers into two forms, which I have endeavoured to estab- 



with basifugal development of leaf -lobes. Here, I find a succession of lobes ^ 

 from a point both upwards and downwards. The upper pair of foliaceous pinnae 

 appears in the first instance ; and, from this, as a point of departure, the cir- 

 rhose pinnas appear in basifugal succession towards the apex of the leaf, 

 while the other foliaceous pinnae appear successively towards its base. Payer 

 has described an analogous succession from a midway-point upwards and 

 downwards, in the serrations of the leaf-lobes in Cannabis sativa (Organogenie, 

 pi. 61, fig. 28 ; with descr. p. 283). 



* Organogenie, pp. 460-1, pi. 98. Payer has, somewhat hastily, I think, 

 compared the compound stamens in the Myrtacese to leaves with lobes 

 developed from base to apex, or basifugally. [Op. cit. p. 718.) His figures 

 however, distinctly indicate that here, as in the ordinary forms of compound 

 stamens, there is a mesial stamen or lobe of the compound stamen, from 

 which, as a point of departure, the evolution of the other stamens extends ; 

 and it appears to me improbable that a basifugal succession of lobes should 

 be initiated by the development of a lobe in the middle line at the base of the 

 compound stamen. The phenomenon seems more naturally explained by 

 supposing that the first developed lobe of the myrtaceous compound stamen 

 corresponds to the first developed or terminal lobe in the ordinary form, in 

 which case the evolution in both forms would be basipetal — the only difier- 

 ence between the two being that, while in the Hypericacese, &c., the lobes 

 are developed on the back or outer face of the rachis of the compound 

 stamen (the staminal cushion), in the Myrtacese they appear on its front or 

 inner face. In confirmation of this opinion, I may refer to the highly developed 

 staminal groups in 3Ielaleuca purpurea, where, in each phalanx, the stamens 

 evidently proceed from the inner face of the flattened and elongated rachis. 

 NEW SERIES.-— VOL. XTX. XO. II. APRIL 1864. 2 K 



