BROOKLYN BOTANIC GARDEN 
LEAFLETS 
THE BROOKLYN INSTITUTE OF ARTS AND SCIENCES 
Series IV Brooklyn, N. Y., June 28, 1916. 
No. 9. 
VARIATION, ENVIRONMENT AND THE 
LAWS OF HEREDITY 
Endless variety is the most striking fact about the planet on 
which we live. Even the great expanses of desert only appear 
monotonous and so undiversified as regards the plant and animal 
life which they support because we unconsciously compare such 
regions with those more richly endowed. So seldom are two 
living things produced exactly alike that their discovery, especially 
among human beings, causes the greatest wonderment. Our 
neighbors and acquaintances are short or tall, with all degrees of 
intermediates between. Their eyes are brown, gray, hazel, blue, 
pink, and a score of undifferentiated intermediate shades. Their 
hair comprises all degrees of diversity in form and color from 
that which hangs in long golden ringlets to that of the deepest, 
straightest black. Their temperaments, as well as almost every 
other character they possess, represent an enormous amount of 
diversity. Even those characters which we commonly are prone 
to think are absolutely unvariable, such as the number of fingers 
and toes, occasionally exhibit variation. In fact there are said to 
be whole families, and in one case a tribe, with more than the 
normal number of fingers and toes. Close relationship, as among 
the members of the same family, does not eliminate this diversity 
of character. How many times are we driven to the most wild 
speculations to account for differences between brothers, between 
sisters, or between children and parents. Some characteristics 
we ascribe to heredity, others we lay to environment, but in many 
cases neither heredity nor environment seem to account for the 
appearance of strange characters. 
In the plant world, as in human beings, exact likenesses are 
rare. And this is true, even when plants are of the same variety, 
coming from seed produced by many generations of inbreeding. 
But what is still more striking is the diversity among plants 
propagated by cuttings, budding, grafting, or by offshoots— 
plants that are only isolated parts of the same plant— as, for ex- 
