ON VARIETIES, RACES, SUB-SPECIES, AND SPECIES. 87 



should be chosen, the origin, external appearance, and conditions 

 of development of which res^emble each other the most. 



(b) Influence of external agents acting in the same place at 

 different times. 



Unusual states of the atmosphere produce unusual effects. 

 As examples of tliis we may mention the following focts com- 

 municated by M. Vilmorin : — 



" I saw," he says, " in a very hot and damp autumn some time 

 ago, all tlie York cabbages of the market-gardens of Bercy and 

 the Faubourg St. Antoine run to seed instead of forming heads, 

 to the great loss of their owners." 



This example sufficiently shows how important it is for 

 market-gardeners to observe the circumstances which are likely 

 to interfere with their business : they should pay great attention 

 to the organ fi-om which the seeds are taken, the time that is in 

 each individual case the most fit for sowing, the manuring of the 

 sown seeds, water, and heat. " If these things were neglected," 

 says M. Vilmorin, " I think that all our heart cabbages, as well 

 as the better sorts, such as the Savoy, cauliflower, Kohl-rabi, 

 &c., would in a few generations come to the condition of the 

 wild green cabbage." 



" Potherbs with curled leaves, such as parsley, cress, &c., 

 even with tiie greatest care are liable to return to their natural 

 state ; they are constantly producing, and sometimes in very con- 

 siderable quantities, individuals with uncurled leaves. 



" All cultivated roots, as carrots, beet, turnips, radishes, are 

 in the same predicament. If the seed-bearing organ be ever so 

 little neglected, in the very first year after the sowing plants will 

 be obtained which will run up, and their roots will be w ithout 

 that substance, fleshy and tender quality pecnliar to the improved 

 race." 



Whilst on the question of causes acting in the same place but 

 at different times, we shall refer to the influence which the ti7ne 

 of sowing may have on one and the same plant, as exemplified in 

 the sowing of the carrot in summer by M. Vilmorin and of the 

 pe-tsai cabbage in August by M. Pepin. The latter gentle- 

 man obtained from seed sown in August, plants with large 

 and closely packed leaves and stalks, some of which weigiied 

 from 4 to 7 pounds in the months of October or November, and 

 which in the following spring produced flowers on branched 

 stems more tlian a yard high, whilst spring-sown seeds gave only 

 a single stem with 4 or 6 leaves, which, after growing to the 

 height of about a quarter of a yard, flow^ered soon after. The 

 sowing is clearly an occasional cause of the modifications of 

 which we speak, for they are owing to the difference of the 

 external conditions to which seeds sown in autumn or spring are 



