1897.] NATURAL SCIENCES OF PHILADELPHIA. 201 



garden rather .shaded, plants from a warm cinder hed, plants under 

 the shade of evergreens, and so on through six others. Though no 

 less than 7,951 flowers in thirteen widely separated genera were ex- 

 amined — 5,700 being of the common chickweed — the author states 

 that the results are "insufficient to establish any fact other than 

 that plants do vary," but supports " the main contention of this 

 paper that the position of the flower on the axu affects the sexual, or- 

 gans if they vary." This is simply my own doctrine on the origin 

 of sexes in flowers 7 given at the Salem meeting of the American 

 Association, that the position of the flower on the axis in relation to 

 the supply of nutrition, or the ability of the organs to avail them- 

 selves of the nutrition provided, decides the character of the sexual 



organs. 



The laborious and valuable observations in these papers result in 

 showing a correlation in appearance and disappearance of stamens 

 and carpels in their variable species. When the stamens were in- 

 creased in numbers there would be an increase in carpels and vice 

 i. A change in one organ resulted definitely in a change in 

 others. This I have observed in the common Dahlia in garden.-. 

 The ray florets in the normal " single form are pistillate, the tubu- 

 lar disk florets are hermaphrodite. In what are termed "double" 

 Dahlias — that is, when the florets become all ray-like or ligulate — 

 the purely female condition follows with the change from tubular to 

 ligulate. I believe this is true in most cases where the tubuli- 

 floral section of Composite assume ligulifloral conditions, as it is a 

 fact well worth noting in connection with this whole subject that 

 while Dahlia, Helianthus, JJe//i--, Chrysanthemum and numerous 

 other species with normally tubulifloral florets will advance occa- 

 sionally to the ligulifloral or so-called double condition of the 

 florists, I can recall no instance of one normally of the latter class 

 that assumed the tubulifloral or " single " condition. 



The observations of Mr. Burkill, as well as my own long-recorded 

 observations, show that the variations in the various organs of 

 plants cannot be accounted for under the chapter of accidents com- 

 monly known as natural selection or conditions of environment ; but 

 are arranged under a definite plan, governed by the degree and con- 

 dition of vital energy, and that this energy itself is dependent on 

 the supply of nutrition, including the life-power of the cells inter- 

 ested to avail themselves of it. 



" -eeProc. Am. Assoc, 18G9 ; also American Naturalist, 1869, p. 260. 



