298 



VAEIATION OF PLANTS AND ANIMALS. [Ch. XXXVI. 



streaked with, black. Mr. Darwin found that a single 

 grain in one variety equalled in weight seven grains of 

 another. The tall kinds grown in southern latitudes and 

 exposed to great heat require from six to seven months 

 to ripen their seed^ whereas the dwarf kinds grown in 



climates 



months."^ 



maize 



farther and farther northward, in which case the changes 

 induced by an alteration of climate have been added to 

 those due to selection. In this plant the results of in- 



acclimatisation 



Met 



m 



Amer 



Germany 



year the plants were twelve feet high and few seeds were 

 perfected. The lower seeds in the ear kept true to their 

 X^roper form^ but the U23per ones became slightly changed. 



from 



to ten 



In the second generation the plants were 

 feet in height, and the seeds had changed from white to yellow 

 and were more rounded in form. In the third generation 

 nearly all resemblance to the original and very distinct 



In the sixth generation this maize, 



■m 



which continued to be cultivated near He 



only be distinguished from the common European kind by 



says 



Mr 



a somewhat more vigorous growth. ^The fact/ 



Darwin, ' affords the most remarkable instance known to me 



of the direct and prompt action of climate on a plant.' 



Several hundred varieties of the vine, each characterised 

 by differences in their fruit, have been reared in hothouses, 

 or cultivated for wine, while the mulberry, both in France 

 and India, has given rise to as many varieties in the texture 

 and quality of the leaves, characters which have been ren- 

 dered constant by selection. 



ment he might doubtless have produced endless changes 

 in the leaves of the vine, the grapes remaining unaltered, 

 and a great many races characterised by different fruits in 

 the mulberry, while the leaves, being neglected, would not 



* Mctzger die Gotreldoarten, 1841, p. 206, cited by Darwin 'On Variation/ 

 vol. 1. p. 321. 



man 



f 



4 



! 



/ 



r."^ 



