314 BOTANY [CHAP. X 



Letter 638 or I had forgotten, that a single frond on a fern will vary ; I 

 now see that the case does come under bud-variation, and 

 must be given by me. I had thought of it only as proof 

 [of] inheritance in cryptogams ; I am much obliged for your 

 correction, and will consult again your paper and Mr. Bridge- 

 man's. 1 I enclose varieties of maize from Asa Gray. Pray 

 do not thank me for trusting you ; the thanks ought to go 

 the other way. I felt a conviction after your first letter that 

 you were a real lover of Natural History. 



If you can advance good evidence showing that bisexual 

 plants are more variable than unisexual, it will be interesting. 

 I shall be very glad to read the discussion which you are 

 preparing. I admit as fully as any one can do that cross- 

 impregnation is the great check to endless variability ; but I 

 am not sure that I understand your view. I do not believe 

 that the structure of Primula has any necessary relation to a 

 tendency to a dioecious structure, but seeing the difference in 

 the fertility of the two forms, I felt bound unwillingly to 

 admit that they might be a step towards diceciousness ; I 

 allude to this subject in my Linum paper. 2 Thanks for your 

 answers to my other queries. I forgot to say that I was at 

 Kew the other day, and I find that they can give me capsules 

 of several Vandese. 



Letter 639 To J. Scott. 



Down, March 24th [1863]. 



Your letter, as every one you have written, has greatly 

 interested me. If you can show that certain individual Passi- 

 floras, under certain known or unknown conditions of life,,have 

 stigmas capable of fertilisation by pollen from another species, 

 or from another individual of its own species, yet not by its 

 own individual pollen (its own individual pollen being proved 

 to be good by its action on some other species), you will add 

 a case of great interest to me ; and which in my opinion 

 would be quite worth your publication. 3 I always imagined 



1 The facts are given in Animals and Plants, Ed. II., Vol. I., p. 408. 



2 Linn. Soc. Journal, 1863. 



3 Cases nearly similar to those observed by Scott were recorded by 

 Gartner and Kolreuter, but in these instances only certain individuals 

 were self-impotent. In Animals and Plants, Ed. II., Vol. II., p. 114, 



