.402 LOCK: STUDIES IN PLANT BREEDING 
conditions frequently very unfavourable, the results ob¬ 
tained by other observers in Europe and America, establish¬ 
ing the excellence and accuracy of Mendel’s work, were on 
the whole fully confirmed. 
Observations were made upon several plants native to the 
tropics, in the hope of discovering suitable objects for 
further experiments. But only a few were found to fulfil 
all the necessary conditions. In the present case a short 
period of growth, reasonable facility of manipulation, and a 
ready success of artificial pollination were essential in 
addition to the requirements postulated by Mendel (49) for 
his experimental plants, viz., the possession of constant 
differentiating characters, facility of protection from foreign 
pollen, and an absence of disturbances in the fertility of 
the cross-bred plants. In fact, like Mendel and Knight (44) 
before me, I have found “ no plant so calculated to answer 
my purpose as the common pea,” although Indian corn has 
also yielded results of considerable interest. 
Work previous to the Rediscovery in 1900 of Mendel’s Papers . 
The following brief historical notes make no kind of 
pretence to completeness. They are intended merely to 
recall a few of the principal steps by which the present 
state of our knowledge has been reached :— 
J. G. Kölreuter (46) was the first to attack the problem of 
inheritance in cross-bred plants by experimental methods. 
As early as 1761 he established the fundamental fact that 
the contribution of the two parents to the offspring is sub¬ 
stantially equal. And in the following years he carried out 
a series of experiments by which his knowledge of hybrid 
plants reached a level which was hardly excelled previous 
to the publication of Mendel’s papers. These experiments 
showed, among a number of other facts now equally familiar, 
that in plants the results of reciprocal crosses are usually 
identical, although not always carried out with equal facility; 
that hybrids between different races of the same species are 
