' Chap. XXIII. CONDITIONS OF LIFE. 275 



and useless. Hemp, on the other hand, fails to produce in England 

 that resinous matter which is so largely used in India as an intoxicating 

 drug. to 



The fruit of the Melon is greatly influenced by slight differences in cul- 

 ture and climate. Hence it is generally a better plan, according to Naudin 

 to improve an old kind than to introduce a new one into any locality' 

 The seed of the Persian Melon produces near Paris fruit inferior to the 

 poorest market kinds, but at Bordeaux yields delicious fruit 12 Seed is 

 annually brought from Thibet to Kashmir," and produces fruit weighing 

 from four to ten pounds, but plants raised from seed saved in Kashmir 

 next year give fruit weighing only from two to three pounds. It is well 

 known that American varieties of the Apple produce in their native land 

 magnificent and brightly-coloured fruit, but in England of poor quality 

 and a dull colour. In Hungary there are many varieties of the Kidney- 

 bean, remarkable for the beauty of their seeds, but the Eev. M J Berkeley" 

 found that their beauty could hardly ever be preserved in England and in 

 some cases the colour was greatly changed. We have seen in the ninth 

 chapter ^ with respect to wheat, what a remarkable effect transports from 

 the North to the South of France, and reversely, produced on the weight 

 oi the gram. 



When man can perceive no change in plants or animals 

 which have been exposed to a new climate or to different treat- 

 ment, insects can sometimes perceive a marked change. The 

 same species of cactus has been carried to India from Canton, 

 Manilla, Mauritius, and from the hot-houses of Kew, and there 

 is likewise a so-called native kind, formerly introduced from 

 South America; all these plants are alike in appearance, but the 

 cochineal insect flourishes only on the native kind, on which it 

 thrives prodigiously. 15 Humboldt remarks 16 that white men 

 "born in the torrid zone walk barefoot with impunity in the 

 same apartment where a European, recently landed, is exposed 

 to the attacks of the Pulex penetrans:' This insect, the too 

 well-known chigoe, must therefore be able to distinguish what 

 the most delicate chemical analysis fails to distinguish, namely, 

 a difference between the blood or tissues of a European and 

 those of a white man born in the country. But the discernment 

 of the chigoe is not so surprising as it at first appears ; for 



J Naudin 'Annales des Sc. Nat.,' » Eoyle, 'Productive Resources of 



4th series, Bot., torn, xi., 1859, p. 81. India,' p. 59. 



' Gardener's Chronicle,' 1859, p. 464. w < Personal Narrative ' En- translat 



" Moorcroffs < Travels,' &c, vol. ii. vol. v. p. 101. This statement has been 



P \! 4 ?- s , ™ . , , confirmed by Karsten ('Beitrag zur 



'Gardeners Chronicle, 1SG1, p. Kenntniss der Rhynchoprion :' Moscow 



1113 - 1864, s. 39), and by others. 



T 2 



