Chap. XXIII. CONDITIONS OF LIFE. 291 



humid than usual. Whether the station was unusually dry or 

 humid, variations adapting the plant in a slight degree for 

 directly opposite habits of life would occasionally arise, as we 

 have reason to believe from what we know in other cases. 



In most, perhaps in all cases, the organisation or constitution 

 of the being which is acted on, is a much more important 

 element than the nature of the changed conditions, in deter- 

 mining the nature of the variation. We have evidence of this 

 in the appearance of nearly similar modifications under different 

 conditions, and of different modifications under apparently nearly 

 the same conditions. We have still better evidence of this in 

 closely parallel varieties being frequently produced from distinct 

 races, or even distinct species, and in the frequent recurrence 

 of the same monstrosity in the same species. We have also seen 

 that the degree to which domesticated birds have varied, does 

 not stand in any close relation with the amount of change to 

 which they have been subjected. 



To recur once again to bud-variations. When we reflect on 

 the millions of buds which many trees have produced, before 

 some one bud has varied, we are lost in wonder what the 

 precise cause of each variation can be. Let us recall the case 

 given by Andrew Knight of the forty-year-old tree of the yellow 

 magnum bonum plum, an old variety which has been propagated 

 by grafts on various stocks for a very long period throughout 

 Europe and North America, and on which a single bud sud- 

 denly _ produced the red magnum bonum. We should also 

 bear m mind that distinct varieties, and even distinct spe- 

 cies -as in the case of peaches, nectarines, and apricots — 

 ot certain roses and camellias,-although separated by a vast 

 number of generations from any progenitor in common, and 

 although cultivated under diversified conditions, have yielded 

 by bud-variation closely analogous varieties. When we reflect 

 on these facts we become deeply impressed with the conviction 

 that m such cases the nature of the variation depends but little 

 on the conditions to which the plant has been exposed, and not 

 m any especial manner on its individual character, but much 

 more on the general nature or constitution, inherited from some 

 remote progenitor, of the whole group of allied beings to which 

 the plant belongs. We are thus driven to conclude that in most 



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