

228 



SELECTION. 



CiiAr. XXI. 



' ' until the other 



ts had first become filled with the knots 



5> 



On the other hand, peaches in North America suffer much 



from a disease called 



yellows, which seems to be peculiar 



that continent, and "more 



of 



U 



when the disease first appeared, were the yellow-fleshed 



peaches 



The white-fleshed kinds are much more 



ely 



attacked ; in some parts of the country 



In Mauritius 



the 



hite 



sugar-canes have of late 



years been so 



ely 



to g 



d by a disease, that many planters have been compelled 



rowing this variety (although fresh plants were 



up 



imported from China for trial), and cultivate only red 

 Now, if these plants had been 



forced to 



le with other 



competing plants and enemies, there cannot be a doubt that the 

 colour of the flesh or skin of the fruit, unimportant as these 

 characters are considered, would have rigorously determined their 



existence. 



Liability to the attacks of parasites is also connected with 



colour. It appears that white chickens are certainly more sub- 

 ject than dark-coloured chickens to the gapes, which is caused 



a parasitic worm in the trachea. 10 







the other hand 



experience has shown that in France the caterpillars which 



produce 



cocoons resist the deadly fungus better than 



those producing yello 

 observed with plants : i 



30ns. 11 Analogous facts have been 

 and beautiful white onion, imported 



from France, though planted close to other kinds 



ed by a parasitic fung 



12 



White verbenas are especially 



liable to mildew. 13 Near Malaga, during an early period of the 

 vine-disease, the green sorts suffered most ; " and red and black 

 grapes, even when interwoven with the sick plants, suffered not 

 at all." In France whole groups of varieties were compara- 

 tively free, and others, such as the Chasselas, did not afford a 



I do not know whether any 



here 



gle fortunate exception ; but 



correlation between colour and liability to disease was 



observed 



In 



former chapter it was shown how 



;ly 



liable one variety of the strawberry is to mildew 



- - - 



9 'Proc. Koyal Soc. of Arts and 

 Sciences of Mauritius,' 1852, p. cxxxv. 



10 • Gardener's Chronicle,' 1856, p. 379. 



11 Quatrefages, 'Maladies Actuelles 

 -du Ver a Soie,' 1859, pp. 12, 214. 



12 ' Gardener's Chronicle,' 1851,p. 595. 



13 ' Journal of Horticulture,' 1862, p. 



476. 



14 « Gardener's Chronicle,' 1852, pp. 



435, 691. 



I 



f 





