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 
mieroscopists 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 Eose bud on a 
Black Currant, under the impression that he could get a black 
Eose; 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—exce£)t 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. 
OBSEEVATIONS ON SOME PLANTS EXHIBITED. 
By the Eev. Prof. G. Henslow, M.A., Y.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 
