1864- -1S69] GRAFT-HYBRIDS 285 



however, has been observed near Heligoland ' ; and land-birds, Letter 205 

 after resting for a time on the tranquil sea, have been seen to 

 rise and continue their flight. I cannot give you the reference 

 about Heligoland without much searching. This alighting on 

 the sea may aid you in your unexpected difficulty of the 

 too-easy diffusion of land-molluscs by the agency of birds. 

 I much enjoyed my morning's talk with you. 



To F. Hildebrand. Letter 206 



Down, Jan. 5th [1868]. 



I thank you for your letter, which has quite delighted me. 

 I sincerely congratulate you on your success in making a 

 graft-hybrid, 2 for I believe it to be a most important observa- 

 tion. I trust that you will publish full details on this subject 

 and on the direct action of pollen 3 : I hope that you will be 

 so kind as to send me a copy of your paper. If I had suc- 

 ceeded in making a graft-hybrid of the potato, I had intended 

 to raise seedlings from the graft-hybrid and from the two 

 parent-forms (excluding insects) and carefully compare the 

 offspring. This, however, would be difficult on account of 

 the sterility and variability of the potato. When in the 

 course of a few months you receive my second volume, 4 you 

 will see why I think these two subjects so important. They 

 have led me to form a hypothesis on the various forms of re- 

 production, development, inheritance, etc., which hypothesis, 

 I believe, will ultimately be accepted, though how it will be 

 now received I am very doubtful. 



Once again I congratulate you on your success. 



1 Instances are recorded by Gatke in his Heligoland as an Ornitho- 

 logical Observatory (translated by Rudolph Rosenstock, Edinburgh, 

 1895) of land-birds, such as thrushes, buntings, finches, etc., resting for 

 a short time on the surface of the water. The author describes observa- 

 tions made by himself about two miles west of Heligoland (p. 129). 



2 Prof. Hildebrand's paper is in the Bot. Zeilung, 1868 : the substance 

 is given in Variation of Animals and Plants, Ed. II., Vol. I., p. 420. 



3 See Prof. Hildebrand, Bot. Zeitung, 1868, and Variation of Animals 

 and Plants, Ed. 11., Vol. I., p. 430. A yellow-grained maize was fertilised 

 with pollen from a brown-grained one ; the result was that ears were 

 produced bearing both yellow and dark-coloured grains. 



4 This sentence may be paraphrased—" When you receive my book 

 and read the second volume." 



