190 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



pollination is now so well understood by gardeners that one 

 need not dwell upon this, except to observe that it was by no 

 means certain fifty years ago which organ was the male and 

 which the female. It required much labour and skill by 

 microscopists to determine that the embryo was a result of 

 impregnation of a germ -cell within the ovary of the pistil by the 

 pollen, and not formed in the pollen-tube itself, as Dr. Schleiden 

 thought. In crossing flowers, as also in grafting, something 

 must be known of the affinities of plants, for both processes 

 will fail if the experimenter transcends a certain amount of 

 affinity. Thus, I have known a gardener graft a Rose bud on a 

 Black Currant, under the impression that he could get a black 

 Rose ; but as they do not belong to the same family the chance of 

 success was very remote and completely failed. On the other 

 hand a gardener may make a lucky hit, as was the case in 

 grafting Garrya elliptica on Aucuba japonica, for it was not 

 then known — except to Sir J. D. Hooker — that they belonged to 

 the same family. Garrya being a curious type had only just 

 before been placed in the same family when the "Genera 

 Plantarum " was published. It was not, therefore, surprising to 

 meet with success ; but the experimenter had no grounds for 

 believing it would succeed, or for anticipating the happy result. 



The few preceding observations and illustrations will be 

 sufficient to show that some knowledge of vegetable physiology 

 is absolutely necessary for a practical horticulturist, and a short 

 course of study will soon awaken the desire to know more. 

 Having learnt of what a plant consists, and what it requires, 

 the gardener must then exercise his judgment and skill in trying 

 to see how he can best supply the conditions to secure its 

 healthy growth and propagation. 



OBSERVATIONS ON SOME PLANTS EXHIBITED. 

 By the Rev. Prof. G. Henslow, M.A., V.M.H., &c. 



[June 28, 1898.] 



Campanulas. — A fine collection of these plants showed how 

 the extra structures of the flowers were made, viz., as follows : — 

 (1) With a second corolla (catacorolla) only ; (2) calyx, as a 



