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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The increased rapidity with which some plants strike by this 

 method leads to the conjecture that the direct rays of the sun have a 

 stimulating influence other than that implied in the heat unit, and are 

 more decisive in promoting energetic growth than the suffused heat 

 derived by the cutting from the water alone. We have not yet made 

 precise comparative experiments bearing on this point, but it has 

 suggested the combining of under-root watering with full insolation. 

 For this preparations are being made. 



I may add one further remark to this account of our methods at 

 Edinburgh in order to emphasize the value of the soil temperature. 

 Our ordinary frames for cuttings are of brick and built against the side 

 of a potting shed, and their base is only a few feet distant from one of 

 the underground four-feet channels conveying leader heating pipes to 

 our plant houses. Although these leader pipes are ensheathed in non- 

 conducting material the temperature of the channel is steadily above 

 that of the air outside, and I have no doubt it affects and contributes 

 to the maintenance of uniformity of the temperature in the soil o'f the 

 frame. This has probably its effect upon the cuttings, and in these 

 frames many cuttings of difficult plants have been struck. 



I have in this lecture confined myself to dealing with some of the 

 matters that seem to touch the foundation of the idea expressed in my 

 text and to an endeavour to show how some at least of the difficulties 

 experienced by propagators are not a consequence of inherent qualities 

 in the plants themselves, and that, therefore, by method in propagation 

 they may be overcome. In what does that method consist? 



(a) In maintaining adequate water-supply in the cutting until it is 

 able to absorb for itself. 



(b) In applying stimuli to encourage the development of the new 

 water- absorbing organs, and to promote the development of the shoot. 



(c) In securing adequate temperature and aeration at the rooting 

 end of the cutting. 



Therein is the essence of propagation by cuttings. 



Much investigation will be required before we are able to prescribe 

 for all desirable plants what is the best procedure for their vegetative 

 propagation from the gardening standpoint. At Edinburgh investiga- 

 tion has been in progress for some years, and I have drawn largely 

 upon the work of Mr. Laurence Baxter Stewart, the enthusiastic 

 plant propagator, whom I am so fortunate as to have on my staff, as 

 well as upon the work of one of my assistants — Miss Bertha Chandler 

 ■ — who has been engaged in preparing a story of principles and 

 methods of propagation in which will be incorporated, with the results 

 of her own experiments, a record of methods advocated by propagators 

 as these are preserved in periodical literature and books on gardening. 

 1 hope that the record will be sufficiently advanced for publishing 

 next year. 



In conclusion, I wish again to express my appreciation of the 

 ■ honour of being invited to address you through these lectures m 

 commemoration of the great horticulturist whose name they bear. 



