200 PROCEEDINGS OF PHE ACADEMY OF [1897. 



duoed, it has not been difficult to prove that the changes, wholly 

 credited to outside conditions, simply hastened the internal action 

 which could have been taken wholly independently of these condi- 

 tions. 



It has fallen to me to show, tirsr in a paper published in the Pro- 

 ceedings of the American Association for the Advancement of 

 Science, 1868, and subsequently in other papers, that form is the 

 result of varying degrees of life-energy, and that the degree of en- 

 ergy is due to the ability of the whole plant or portions of a plant, 

 to elaborate nutritive material. This being true, external condi- 

 tions may have to do with the supply or the character of plant 

 nutrition, but it is the constitutional power of a plant, or any por- 

 tion of a plant, to avail itself of nutrition that determines the result- 

 ing lite-energy. 



The present paper has been suggested by reading an excellent 

 memoir in the Linnean Society's Journal, Botany, Vol. XXXI. 5 

 It starts out with this proposition: "The capability of varying is 

 admittedly a general property of all living organisms, but how 

 variation is affected by forces other than natural selection we know 

 but little." 



I have shown in my address before the American Association at 

 its Montreal meeting,''' that variation is an essential condition in the 

 general order of things, and that the reasons for the innumerable 

 variations in the forms of leaves and flowers must be sought for in 

 the necessity of variety for variety's sake, and not in the mere acci- 

 dent of external conditions. In other words the internal enemies 

 of the plant, varying as they do in results from their varying de- 

 grees, would produce innumerable variations, although the external 

 conditions u ■ idly the same all over the world. 



In this paper and another correlated in the Journal of Botany 

 for January. 1896, Mr. "Burkill records the results of patient and 

 careful studies of variations in the number of stamens and carpels 

 of several species of plants in which these variations have been con- 

 spicuously known. But he starts with supposition already referred 

 to, that different external conditions govern the results, lie. there- 

 fore, divides his examination of the common chiekweed into classes 

 accordingly: plants from hayfields, damp locality, plants from a 



'a some Variations in the number of Stamens and Carpels, bv I. II. Bur- 

 kill. 

 ' •• Variation in Nature," Vol. for 1871, p. 392. 



