APPENDIX. 4.97 
Balfour kindly wrote as follows in reply to an inquiry respecting this 
plant :— A double white hawthorn in the Royal Botanic Gardens pro- 
duced double flowers in spring. It retained its leaves during autumn 
and winter, until the following spring. It then flowered in the second 
spring, but produced weak single flowers only, and has continued to do 
so ever since. The flowering has been always weak, since this change 
of flowers from double to single. Mr. M‘Nab attributes the change in 
the duration of the leaves to the filling up of the ground round the 
tree, to the height of a foot and a half on the stem. He is now trying 
the effect of extra manure in giving extra vigour to the plant.” Here, 
at least, the production of single flowers would seem to be the result 
of debilitating causes, connected with the unusual persistence of the 
leaves, &c., for while the tree was healthy, double flowers were pro- 
duced. 
A similar illustration came under the writer’s own notice. Some 
seedling balsams, of a strain which from long selection and hereditary 
tendency produces, year after year, double flowers were, in the spring 
(of 1866), allowed to remain ijn the seed-pans for many weeks after 
they were ready to be potted off; they were hence partly starved, and 
when they bloomed, they produced single flowers only. But these same 
plants, when more liberally treated, produced an abundance of double 
flowers. Moreover, other seedlings of the same batch, but sown later, 
and potted off at the usual time, produced double flowers as usual. Of 
a like character is the fact that the double Ranwneulus asiaticus loses 
its doubleness if the roots are planted in a poor soil. 
On the other hand, the way in which double stocks are stated to be 
produced at Erfurt, viz.: by giving the plants a minimum supply of 
water, and the other circumstances alluded to as showing the connection 
between the production of double flowers, and a deficiency of water, as 
well as the experiments of Mr. Monro, go to show that, so far from 
plethora, the inducing cause must be more nearly allied to inanition, 
though the impoverishing process is, to a certain extent, counteracted 
by only allowing a few of the seed-pods to ripen, and thus concentrating 
in a small number of flowers the nutriment intended for many. 
Professor Edward Morren (‘ Bull. Acad. Roy. Belg.,’ 2me ser., vol. 
xix, p. 224) considers the existence of true variegation in leaves, and the 
production of double flowers, as antagonistic one to the other; the 
former is a sign of weakness, the latter of strength. But it would 
seem that the exceptions are so numerous—so many cases of the co- 
existence of variegated leaves, and double flowers are known, at least in 
individual plants if not in species—that no safe inferences can be drawn 
as to this point. Since the above remarks were printed, Professor 
Morren has published a second paper on the subject, upholding his 
former views as to the incompatibility of variegated foliage (not mere 
colouration) and double flowers. In this paper he criticises the ob- 
32 
