two wild South American species. Only after careful isolation of 
single plants and several generations of purification by inbreed- 
ing does like begin to produce like. By such methods variability 
is reduced to a minimum, and a comparatively pure breeding 
strain or variety created. 
For centuries scientific men have grappled with this problem 
of variation, attempting to discover some law or order in all the 
seeming chaos that it produces. When certain characters were 
common to both parent and offspring they called it heredity, but 
often other characters appeared — characters that had been un- 
unknown to the ancestral line for generations. The breed of 
chickens called BlueAndalusian presented an extremely perplexing 
problem, as about one-fourth of the eggs always produced sooty 
whites, and another fourth black chickens, only one-half being- 
typical Andalusian. No amount of selection and inbreeding 
reduced the number of these off-types. Such cases made men 
despair of finding any laws of heredity or variation. As soon as 
one was formulated, innumerable exceptions arose which shortly 
proved the law a fallacy. Superstition was common. Straw- 
berry-like birth marks appeared on children because the mother 
had seen or dreamed of strawberries preceding its birth. Hours 
were spent before beautiful statues and paintings, that the unborn 
child might be beautiful. The breeding of fine mares to scrub 
or undesirable stallions for a single time was supposed later to 
mar the offspring of these same mares by fine stallions. Experi- 
ments by scientific men were few and far between and largely 
resulted in collections of interesting but isolated facts. What 
was specially needed was some one who could arrange and corre- 
late these facts into a general law. “Heredity,” wrote Balzac, “is 
a maze in which science loses itself.” 
Then came the Austrian monk, Gregor Mendel, a man with a 
mathematical, analytical mind. With the insight and persever- 
ance characteristic of genius, he outlined some experiments 
which he believed would throw light on the inheritance of charac- 
ters and bring order out of chaos. After much experimenting, he 
selected peas as the material most favorable for his purpose, 
made certain that the varieties bred true in certain well-defined 
characters, and proceeded with some crossing experiments be- 
tween varieties differing from each other in one or more of these 
tested, true-breeding characters. When a plant with reddish- 
purple flowers was crossed with one having white flowers, the 
offspring were not pink, as one might naturally expect, but all 
were reddish-purple flowered. When the seed of any one of these 
reddish-purple flowered plants was planted, both white and col- 
ored-flowered plants were produced in the ratio of one with white 
flowers to three with colored flowers. All the whites and approx- 
imately one-third of those having colored flowers bred true to 
their respective colors in the next or third hybrid generation 
(F 3 ). The other colored-flowered plants (approximately two- 
thirds of all those with colored flowers) produced seed which 
again gave the ratio of three with colored flowers to one with 
white flowers. From extensive experiments tried since, involving 
large numbers, we have every reason to believe that two-thirds of 
those with colored flowers from such a cross after the first genera- 
tion would always produce plants with colored flowers and plants 
with white flowers in approximately the three to one ratio. Other 
pea characters, amounting to twelve in all (six pairs) , were tested 
by Mendel in this manner, and the results they gave agreed with 
those of the experiment just cited. These included such charac- 
ters as the color of the seedcoat, the color and shape of the 
cotyledons, the height of the plants, the color of the pods, and 
