in Plant Cytology. 201 



merited with, the coloration effects during succeeding years 

 can be made to vary according to the degree of illumination. 

 Least pigmented of all the native species is 6". variolaris, 

 which, in the shade, is a pale green, but in hot sunny meadows 

 may show a reddish yellow flush. Historically it may be 

 noted that John Bartram recorded similar color relation in 

 wild plants of Dioncsa. My experiments on this plant prove, 

 that the deep crimson pigment, developed in the cells of the 

 leaf glands, equally responds to environmental treatment as do 

 the Sarracenias. 



But similar results may be obtained from totally different 

 environmental stimuli. Botanists who have only seen Mimosa 

 pudica grown under glass with direct insolation, and at a 

 temperature of 30°-35° C. might on first glance fail to 

 recognize an individual of the species that had grown for 

 some weeks in the open, during spring or autumn. Exposure 

 to cold night winds causes the stems, petioles and midribs to 

 assume a brick red hue that gives a new character to the 

 plants. On a large scale we see the same change annually 

 produced, when acres of GuaWicna, Kalmia angustifolia, 

 Cassandra, and many other perennially winter-green plants 

 are exposed to the drying winds and cold temperatures of 

 winter. 



Experiments even which may appear unnatural, often throw 

 a flood of light on cytological questions. Thus Townsend's 

 experiments on lacerated cells and those of Mottier on the 

 effects of centrifugal force, though in themselves unlikely to 

 occur in nature on a large scale, suggest points as to the rela- 

 tive density, resistance, and vitality of cells or cell parts which 

 are of highest import. A perusal of Daniel's successive papers 

 on graft unions reveals a healing and regenerative capacity of 

 cells that is often paralleled in nature by the healing surfaces 

 of stems and roots. But Daniel's work brings the student of 

 cytology face to face with the deepest problems of heredity ; 



