1 862.] ON PLANTS OF THE SAME SPECIES.' 303 



In an article, * Dimorphism in the Genitalia of Plants ' 

 (' Silliman's Journal/ 1862, vol. xxxiv. p. 419), Dr. Gray points 

 out that the structural difference between the two forms of 

 Primula had already been defined in the ' Flora of N. America/ 

 as dioecio- dimorphism. The use of this term called forth the 

 following remarks from my father. The letter also alludes 

 to a review of the ' Fertilisation of Orchids' in the same 

 volume of ' Silliman's Journal.'] 



C. Danvin to Asa Gray. 



Down, November 26 [1862]. 



My dear Gray, — The very day after my last letter, 

 yours of November 10th, and the review in ' Silliman/ which 

 I feared might have been lost, reached me. We were all very 

 much interested by the political part of your letter ; and in 

 some odd way one never feels that information and opinions 

 printed in a newspaper come from a living source ; they seem 

 dead, whereas all that you write is full of life. The reviews 

 interested me profoundly ; you rashly ask for my opinion, 

 and you must consequently endure a long letter. First for 

 Dimorphism ; I do not at present like the term " Dicecio- 

 dimorphism ;" for I think it gives quite a false notion, that 

 the phenomena are connected with a separation of the sexes. 

 Certainly in Primula there is unequal fertility in the two 

 forms, and I suspect this is the case with Linum ; and, 

 therefore, I felt bound in the Primula paper to state that it 

 might be a step towards a dioecious condition ; though I 

 believe there are no dioecious forms in Primulaceae or Linaceae. 

 But the three forms in Lythrum convince me that the 

 phenomenon is in no way necessarily connected with any 

 tendency to separation of sexes. The case seems to me in 

 result or function to be almost identical with what old 

 C. K. Sprengel called " dichogamy," and which is so frequent 

 in truly hermaphrodite groups ; namely, the pollen and stigma 



