496 APPENDIX. 
single blooms, and the desired result is obtained. This is Messrs. 
Windebank and Kingsbury’s modus operandi, the exact process or mode 
of accomplishment being, however, a professional secret.! 
From what has been said, as well as from other evidence which it is 
not necessary to detail in this place, it may be seen that the causes 
assigned by physiologists, and the plans proposed by cultivators for the 
production of double flowers, are reducible to three heads, which may 
be classed under Plethora, Starvation, and Sterility. These three seem 
inconsistent one with the other, but are not so much go as they at first 
sight appear to be. 
The advocates of the plethora theory have much in their favour: 
for instance, the greater frequency of double flowers among cultivated 
plants than among wild ones. The great preponderance of double 
flowers in plants derived from the northern hemisphere, when con- 
trasted with those procured from the southern, as alluded to by 
Dr. Seemann, seems also to point to the effect of cultivation in 
producing these flowers. Now, although this is, to a large extent, 
due to the selection that has been for so long a period practised 
by gardeners, still that process will not account for the appearance 
of double flowers where no such selection has been exercised ; 
as in the case of wild plants. Some double peas, observed by Mr. 
Laxton, appeared suddenly; they had not been selected or sought for, 
but they were produced, as it would appear, as a result of high cultiva- 
tion, and during the period when the plant was in greatest vigour; and 
as the energies of the plant failed, so the tendency to produce double 
flowers ceased. Indeed, in reference to this subject, it is always impor- 
tant to bear in mind the time at which double flowers are produced ; 
thus, an annual plant subjected to cultivation will, it may be, produce 
single flowers for the first year or two, then a few partially double 
flowers are formed, and from these, by careful selection and breeding, a 
double-fiowered race may be secured. Sometimes, as in the peas before 
alluded to, in the same season the earlier blossoms are single, while 
later in the year double blossoms are produced. This happens, not only 
in annuals, but also in perennials, and is not infrequent in the apple; an 
illustration of this occurrence in this tree is given in the ‘ Gardeners’ 
Chronicle’ for 1865, p. 554.2. Sometimes the flowers on a particular 
branch are double, while those on the rest of the plant are single.’ 
On these points, the evidence furnished by a double white hawthorn 
in the Royal Botanie Gardens at Edinburgh is important. Professor 

1 «Gard. Chron.,’ 1867, p. 381.—Art. “ Chinese primroses.” 
2 See also p. 79, ‘fig. 36. A similar flower is figured in ‘ Hort. Eystett. 
Ic. Arb. Vern.,’ fol. 5. “Fructus nondum observatus est fortassis ali- 
mento uberius in flores refuso, nullus sperari possit.” 
* See De Candolle, ‘Plant. Rar. Genev.,’ 1829, p. 91; ana Alph. de 
Candolle, ‘ Géog. Bot.,’ p. 1080. 
