APPENDIX. 499 



tive action is stopped, at least partially pretty much as it Avould b3 if 

 the plant were placed in the opposite condition of starvation. The 

 effect of supplying a plant (or an animal) with an excessive supply of 

 food, which it cannot assimilate, is in many respects similar to that 

 which results from partially cutting off the supplies. And the same 

 reasoning applies to sterility. If by high culture, or the supply of an 

 undue quantity of nourishment, the constitution of the plant bo im- 

 paired, or if the plant be pampered, it is no wonderful thing that sterility 

 should ensue. Hence, then, may it not be asserted as a general principle 

 that in the production of double flowera a partial arrest of development, if 

 not of growth, however produced, is an essential preliminary ? All the 

 attendant phenomena, such as the obliteration of the stamens, the 

 augmentation in the number of floral whorls, the occurrence of pi-olifi- 

 cation, are consistent with the supposition of a primary airest of 

 development, more or less complete, as the case may be : at one time 

 permanent, at another time relaxed and intei'mittent, or in a thii-d set 

 of cases the vegetative activity or power of growth may be restored, and 

 from the centre of the flower may spiing a perfect branch with perfect 

 leaves, the production of sheaths only being superseded by the develop- 

 ment of leaves, in which all the parts sheath, staJk, and blade are 

 present. 



When once the disposition to fonu double flowers is established, that 

 tendency becomes hereditary ; there are races of single Stocks in which, 

 out of hundreds of plants, scai'cely one double-flowered form is met 

 with ; but when the tendency to produce double blooms is set up, single 

 flowers become the exception : thus, in the Balsams, before mentioned, 

 not one in fifty now produces single flowers, and the seeds of these 

 double Balsams pi'oduce double-flowered seedlings, with scarcely a 

 '' rogue " among them. 



The following list of plants producing double flowers of any kind 

 is taken from that given in ' Seemann's Journal of Botany,' vol. ii, p. 177, 

 and to which some additions have been made. Miscalled double flowers, 

 such as those of the CoinpoaUce, Viburnum Hydrangea, &c., ai-e excluded. 



RaJUVTHCXTLJlCTBX. 



Clematis Viticella, Linn., S. Europe. 



florida, Thunb., Japan. 



Fortunei, Moore, tfapan. 



patens, Dcsne, Japan. 

 Anemone japonica, Sieb. et Zucc, Japan. 



coronaria, Xt'nn., S. Europe, Asia Minor. 



hortensis, var. Linn., S. Europe. 



palmata, Linn., N. Africa, Spain, Portugal. 



nemorosa, Linn., Europe, N. America, Siberia. 



sylvestrig, Linn., S. Europe, Sibeiia. 



