APPENDIX. 497 



Balfour kindly vn'oic 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 (lowering 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 gi'ound round the 

 tree, to the height of a foot and a half on the stem. He is now trying 

 the eff'ect 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 wei'e pro- 

 duced. 



A similar illustration came under the writer's own notice. Some 

 seedling balsams, of a strain which from long selection and hereditai*y 

 tendency produces, year after year, double flowers were, in the spring 

 (of 1866), allowed to remain in 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 Ranunculus asiaticus loses 

 its doubleness if the roots are planted in a poor soil. 



On the other hand, the way in which double stocks ai-e 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 expeiiments 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 flowei"s the nutriment intended for many. 



Professor Edward MoiTen (' Bull. Acad. Roy. Belg.,' 2me ser., vol. 

 xix, p. 224) considers the existence of true variegation in leaves, and the 

 production of double flowei-s, 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- 



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