i862 1881] MELASTOMADS 293 



individuals of the same species as worked out in Cross and Self Fertili- 

 sation^ for it is difficult to believe that the pollen of the purple anthers has 

 become, by adaptation, less effective than that of the yellow anthers. In 

 the letters here given there is some contradiction between the statements 

 as to the position of the two sets of stamens in relation to the sepals. 

 According to Eichler (Bliithendiagramme^ II., p. 482) the longer stamens 

 may be either epipetalous or episepalous in this family. 



The work on the Melastomads is of such intrinsic importance that 

 we have thought it right to give the correspondence in considerable 

 detail ; we have done so in spite of the fact that Darwin arrived at no 

 definite conclusion, and in spite of an element of confusion and unsatis- 

 factoriness in^the series of letters. This applies also to Letter 629, written 

 after Darwin had learned Fritz Miiller's theory, which is obscured by 

 some errors or slips of the pen. 



To G. Bentham. Letter 620 



Down, Feb. 3rd [1862?] 



As you so kindly helped me before on dimorphism, will 

 you forgive me begging for a little further information, if in 

 your power to give it? The case is that of the Melastomads 

 with eight stamens, on which I have been experimenting. 

 I am perplexed by opposed statements : Lindley says the 

 stamens which face the petals are sterile ; Wallich says in 

 Oxyspora paniculata that the stamens which face the sepals 

 are destitute of pollen ; I find plenty of apparently good 

 pollen in both sets of stamens in Heterocentron [Heeria], 

 Monochcetum, and Centradenia. Can you throw any light on 

 this ? But there is another point on which I am more 

 anxious for information. Please look at the enclosed miser- 

 able diagram. I find that the pollen of the yellow petal- 

 facing stamens produce more than twice as much seed 

 as the pollen of the purple sepal-facing stamens. This 

 is exactly opposed to Lindley's statement viz., that the 

 petal-facing stamens are sterile. But I cannot at present 

 believe that the case has any relation to abortion ; it is 

 hardly possible to believe that the longer and very curious 

 stamens, which face the sepals in this Heterocentron , are 

 tending to be rudimentary, though their pollen applied to 

 their own flowers produces so much less seed. It is con- 

 formable with what we see in Primula that the [purple] 

 sepal-facing anthers, which in the plant seen by me stood 

 quite close on each side of the stigma, should have been 

 rendered less fitted to fertilise the stigma than the stamens on 



