240 Dr Dickson on Diplostemonous Floivers, dec. 



Before these plants were examined organogenically, the 

 outer stamens were, not unnaturally, assumed to be the 

 older; and, as this involved a w^ant of due alternation of 

 parts, it was imagined that a third and outermost whorl of 

 stamens alternating with the petals must have aborted, the 

 idea being held to be countenanced by the frequent occur- 

 rence, in these plants, of five glands outside the andrcBcium 

 and alternating with the petals.* When, however, the de- 

 velopment of the parts was observed, the unsoundness of 

 this theory became evident ; for it was found that the outer 

 stamens are the younger ; and, moreover, that the glands 

 do not appear until shortly before the time of blossoming. f 



The fact of the younger whorl of stamens being external 

 to the older one is remarkable, as being exactly the reverse 

 of wdiat one would, a priori, have expected. The question as 

 to how stamens should be so arranged, is an interesting one, 

 and derives great importance from the researches of Payer 

 having shown that this arrangement, so far from being un- 

 common, obtains in the greater number of diplostemonous 

 dicotyledons. 



In attempting an explanation of this difliculty, I am fully 

 aware of the delicacy of the questions involved ; and I 

 would offer the result of my consideration of the subject, 

 more as a suggestion worthy of being kept in view by those 

 who may examine diplostemonous flowers, organogenically 

 or otherwise, than as a definite solution of the problem. In 

 short, I would submit -a. possible solution, to be substantiated 

 or negatived by more extended and comprehensive observa- 

 tion of the facts. 



Of dij^lostemonous flowers, there are two principal forms 

 which demand our attention : — 



1st, That in which the younger staminal whorl is the 

 more internal, and the carpels, when of the same number, 

 alternate with the younger stamens. Examples — CoriariaX 



* Maout, Atlas de Botanique, p. 60. Balfour, Class-Book of Botany, p. 783. 

 fig-, 1485, with description. 



t Payer, Organogenie, p. 69 ; pis. 12 and 13 : the development of the glands 

 in Erodium is shewn in pi. 12, figs. 17 and 21. 



X Ibid., p. 49 ; pi. 10. Limnanthes, in all probability, comes under the 

 aame head. Although Payer describes the younger stamens in L. Douglasii 

 as the more external, his figure (pi. 10, fig. 21) does not seem to bear out 



