476 BOTANICAL GAZETTE | JUNE 
Artificial pollination to produce variations in color and the striking regulari- 
ties that appeared in hybrid forms from the same crosses were the special 
features of Mendel’s work, which had for its object a study of the develop- 
ment of hybrids in their offspring. Mendel is not surprised at the new 
discovery of a generally valid law for the formation and development of 
hybrids, considering the great difficulties involved. No previous work, as he 
points out, was carried on in such a manner as to allow of the determination 
of the number of the different forms in which the offspring of hybrids appear, 
and to show that these forms can be classified with certainty in the several 
generations and the mutual numerical conditions determined ; although such 
comprehensive study is the only way finally to solve a question which, in the 
evolution of organic forms, is of no mean importance. 
The reasons for selecting the genus Pisum are given, and from thirty- 
four varieties of peas twenty-two were selected for the experiments, after a 
two-year test had shown them to be constant in their offspring. To study the 
changes in the inheritance of ——— >a maraniey and to determine the- 
law according to which these differences appear in the succeeding gener- 
ations, were the objects of the cat and the latter object would 
_ constantly: divide itself into as many experiments as there were constant 
characteristics i in the plants selected. Of such characteristics there 
differences in the shape of the ripe seed; differences i in 
r of the unripe pods ; differences in the 
CES | in ‘the = of the axes. 
