in Plant Cytology. 201 
mented 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 S. 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 Dionga. 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 AZimosa 
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 orautumn. 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. Ona large scale we see the same change annually 
produced, when acres of Guwaltheria, 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 highestimport. 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 ; 
