372 BOTANY [CHAP. XI 



Letter 694 With respect to the men who have recently written on the 

 crossing of plants, I can at present remember only Hildebrand, 

 Fritz Miiller, Delpino, and G. Henslow ; but I think there are 

 others. I feel sure that Hildebrand is a very good observer, 

 for I have read all his papers, and during the last twenty 

 years I have made unpublished observations on many of the 

 plants which he describes. [Most of the criticisms which I 

 sometimes meet with in Ffench works against the frequency 

 of crossing I am certain are the result of mere ignorance. 

 I have never hitherto found the rule to fail that when an 

 author describes the structure of a flower as specially 

 adapted for self-fertilisation, it is really adapted for crossing. 

 The Fumariacea^ offer a good instance of this, and Treviranus 

 threw this order in my teeth ; but in Corydalis Hildebrand 

 shows how utterly false the idea of self-fertilisation is. This 

 author's paper on Salvia 1 is really worth reading, and I have 

 observed some species, and know that he is accurate]. 2 

 Judging from a long review in the Bot. Zeitung* and from 

 what I know of some of the plants, I believe Delpino's article 

 especially on the Apocyneae, is excellent ; but I cannot read 

 Italian. Perhaps you would like just to glance at such pamphlets 

 as I can lay my hands on, and therefore I will send them, as 

 if you do not care to see them you can return them at once ; 

 and this will cause you less trouble than writing to say you do 

 not care to see them. With respect to Primula, the one point 

 about which I feel positive is that the Bardfield 4 and common 

 oxlips are fundamentally distinct plants, and that the com- 

 mon oxlip is a sterile hybrid. I have never heard of the 

 common oxlip being found in great abundance anywhere, 

 and some amount of difference in number might depend on 

 so small a circumstance as the presence of some moth which 

 habitually sucked the primrose and cowslip. To return to the 

 subject of crossing : I am experimenting on a very large 

 scale on the difference in power and growth between plants 



1 Hildebrand, Pringsheitrfs Jahrbiicher, IV. 



2 The passage within [ ] was published in the Life and Letters, III., 

 p. 279. 



3 Hildebrand's paper in the Bot. Zeitung, 1867, refers to Delpino's 

 work on the Asclepiads, Apocyneas and other Orders. 



4 For a general account of the Bardfield oxlip (Primula elatior} see 

 Miller Christy, Linn. Soc.Journ., Vol. XXXIII., p. 172, 1897. 



