9 ] 



11. 



THE HISTOEY OF THE LONDON PLANE, PLATANUSACERIFOLIA, 

 WITH NOTES ON THE GENUS PLATAN US. 



By AUGUSTINE HENRY, M.A., F.L.S.; 



AND 



MAEGAEET G. FLOOD, B.A. 

 Plates IV-IX. 



Reail Feiiruauy 10. I'ublislied April H, 1919. 



In an article on the " Artificial Production of Vigorous Trees,"^ published in 

 1914, I drew attention to certain well-known trees, like the Lucombe Oak) 

 Huntingdon Elm, Cricket-bat Willow, and Black Italian Poplar, which owe 

 their vigour and botanical characters to the fact that they are of hybrid 

 origin. Such hybrids arose as chance seedlings, due to cross-pollination of 

 two trees of different species growing together. The introduction into Europe 

 during the seventeenth century of North American trees which grew along- 

 side similar but distinct European species in parks and gardens, was the 

 occasion of considei'able hybridization. Trees like the Black Italian Poplar 

 and the London Plane, which have never been seen anywhere in the wild 

 state, are intermediate in botanical characters between an American and a 

 European species in each case, and are undoubtedly first crosses. 



The London Plane, Platanus acerifolia, W., has all the peculiarities which 

 are met with in a first cross. It is intermediate in fruit and leaves between 

 tlie supposed parents — the Oriental Plane, which is indigenous in Greece and 

 Asia Minor, and the Occidental Plane, which grows in a wild state in the 

 forests of the eastern half of the United States. Its vigour is exceptionally 

 great, as is usual in hybrids of the first generation ; and its seeds when sown 

 produce a mixed and varied crop of seedlings, in which are variously combined 

 the characters of the two parents. Several supposed forms of the London 

 Plane which are not uncommonly cultivated, appear to be chance seedlings 

 of this tree, being hybrids of the second generation. 



The vigour of the London Plane is remarkable. It is extensively used 

 for planting in the streets of towns in Europe and North America, as it has 



' Juiu-n. Dept. Agiic, Ireland, xv, pp. 34-52. (Oct., 19U.) 



K.I.A. PKOC, VOL. XXXV, SECT. B. \_B] 



