III. 

 Bud- Variation and Evolution. 



MR. L. H. BAILEY has lately published an interesting paper on 

 this subject,^ treating the well-known phenomenon of bud- 

 variation from rather a novel point of view. He observes that the 

 evolution of the higher animals, at least, has proceeded in accordance 

 with a different law from that of plants, and it is the object of his 

 paper to emphasise the recognition of the fact of asexual evolution in 

 the vegetable kingdom. When we remember that, on the ascending 

 scale of life, the whole of the vegetable kingdom has never risen 

 much above the level of corals, inasmuch as well nigh any portion of 

 the highest plant is capable of reproducing all the phenomena of 

 the entire plant, his contention seems feasible. He observes : " The 

 mere fact that the phyton [or assumed plant unit] may reproduce 

 itself is not the most important point, but rather, that each part of the 

 plant may respond in a different manner or degree to the effects of 

 environment." As no two peas are precisely alike, so no two branches 

 on the same tree are identically the same in every point of structure ; for, 

 " variation among the sisterhood or colony of branches is determined 

 by very much the same conditions which determine variation in 

 independent plants growing in the soil. I believe that the primary 

 and most important determinant of this variation is the variation in 

 food supply." Hence follows a struggle for existence among the 

 developing buds of a tree, strictly parallel to that among a number 

 of individuals growing thickly together. There are weakly developing 

 branches and strong branches, and " the survival of the fittest [i.e., 

 the constitutionally strongest] is Nature's method of pruning." 



With regard to bud-variation, properly so called, which involves 

 not merely vigour — even if it have that — but some change in form 

 and appearance of the organs it may bear, Mr. Bailey shows that 

 there is abundant asexual variation, and that this variation takes 

 place as readily when the phyton is growing upon a plant as when 

 growing in the soil. Now, every branch or phyton is in an incipient 

 degree, a bud-variety ; i.e., as a rule, only in minute or inconspicuous 

 features. Nevertheless, even in these, the practical horticulturist 



i"The Plant Individual in the Light of Evolution." Address before the 

 Biological Society of Washington, January 12, 1S95. (Science, new series, vol. i., 

 p. 281, March 15, 1895.) 



