258 THE ORCHID REVIEW. [SEPTEMBER, 1969. 
disappointing to read, a few lines further on, that “ for fanciers Mendelism 
can as yet do comparatively little . . . two things only. First, . . . it will 
provide a most fascinating pursuit, which if followed with assiduous care 
may at any moment lead to some considerable advance in scientific know- 
ledge. Secondly, the principles already ascertained will be found of 
practical assistance in the formation of new breeds, and may save many 
mistakes and waste of time. But applied to the business of breeding 
winners in established breeds they cannot materially help, for almost always 
the points which tell are too fine to be dealt with in our analysis.”’ 
But what is Mendelism? Several attempts have been made to define 
it, and we have read of Mendel’s Laws of Dominance, of Segregation and 
of Purity. But we are now told that “the dominance of certain characters 
is often an important but never an essential feature of Mendelian heredity. 
Those who first treated of Mendel’s work most unfortunately fell into the 
error of enunciating a ‘Law of Dominance’ as a proposition comparable 
with the discovery of segregation. Mendel himself enunciates no such law. 
. + + Mendel’s principles of inheritance apply equally to cases where 
there is no dominance.’”’ Mendel’s real discovery is thus defined. ‘‘ The 
fact of segregation was the essential discovery which Mendel made.” 
This brings us to Mendel’s original paper. He there alludes to the 
numerous careful observers who had devoted a part of their lives to 
experiments in plant hybridisation, but expresses the conviction that none 
of these experiments had been “‘ carried out to such an extent and in such a 
way as tomake it possible to determine the number of different forms under 
which the offspring of hybrids appear, or to arrange these forms with 
certainty according to their separate generations, or definitely to ascertain 
their statistical relations.”” The paper records the results of such a detailed 
experiment, carried out for eight successive years with the genus Pisum. 
We cannot follow him through these experiments, but may remark 
that they were made by first crossing forms which differed in certain well 
marked characters, thus obtaining hybrids, and then self-fertilising the 
hybrids for several generations and classifying the results. At the same 
time he carefully self-fertilised the original parents to test their constancy. 
The results are well known, and we may summarise his conclusions with 
respect to the fundamental process ot reproduction. 
For the purpose of sexual propagation he points out that one pollen cell 
and one egg cell unite into a single cell, which is capable by assimilation 
and formation of new cells of becoming an independent organism. This 
development follows a constant law, which is founded on the material 
composition and arrangement of the elements which meet in the cell in a 
vivifying union. If the uniting cells be of the same kind and agree with the 
foundation cell {fertilised ovum] of the mother plant, the development of 
