Periodical Literature 97 



diameter. These were girdled to a depth of 8 centimeters, and 

 the trees still bore foliage a year and a half later. The trunk of 

 an oak fifty years old was girdled into the heartwood, and its 

 foliage withered in a few days. Another oak of the same age, 

 which was cut similarly but not quite through the sapwood, did 

 not wither for some weeks. The trunk having been cut to the 

 heartwood in a tree of Prunus avium, and in a Robinia, wilting 

 of the leaves took place in two days in the first case and in a few 

 hours in the second." 



The Ringing of Trees. Gardeners' Chronicle, 14 November, 1914, pp. 

 320-321. 



This paper is a summary account of 



Artificial Professor Henry's experiments of the last 



Production four years in the production of new trees by 



of hybridization. The end in view was to 



Vigorous Trees show that new fast-growing species could be 



obtained. The basis of experiment was 



the exceptional vigor often shown by first crosses. 



The most striking success has been among the poplars. Very 



vigorous growth (10 feet in two seasons) has been shown by hybrid 



seedlings raised from seed of P. angulata fertilized by P. trichocarpa ; 



the hybrid has been named P. generosa by its originator. It is 



worthy of note that the two parents belong to different subsections 



of the genus. A corresponding hybrid with P. nigra betulifolia 



as the male parent showed much less vigor. 



Numerous crossings made with Alnus present some interesting 



features, the seedlings being now three years old. Alnus cordata X 



A. glutinosa japonica produced a hybrid seedling of much faster 



growth and more frost resistant than pure seedlings of the female 



parent. It is already 5 feet high. Various other crosses showed 



evidence of similar vigorous growth, averaging nearly two feet 



in height growth annually. The failures are recorded also. 



Since the first cross does not come true from seed, these hybrids 



can only be propagated vegetatively by cuttings, layerings or 



grafts. 



A complete Hst is given of the various crosses that have been 



tried, with results. These include Fraxinus, Ulmus, Fagus 



Quercus, Larix, Cupressus, Chamaecyparis. 



Journal of the Department of Agriculture and Technical Instruction for Ireland. 

 Volume XV, No. 1. 



