166 THE ORCHID REVIEW. [Nov.-DEc., 1919. 
For it was our correspondent’s enquiry that caused us to look up the 
information given at page 194. 
Another Orchidist asks for particulars about Mendelian hybridisation, by 
which it is said to have been ‘‘ possible to combine in one stock the valuable 
characters of several.” We do not know this particular brand, unless it 
includes the undesirable characters also. He further asks, very pertinently, 
‘*“What is Mendelism?” and cites two recent definitions. One exponent 
says: ‘* The foundation of the Mendelian principle lies in the fact that there 
are pairs of alternating characters, or allelomorphs, related to each other in 
such a way that the reproductive cells bear one or other of these 
characters, but not both. ‘‘Another speaks of the hereditary items 
contributed by two parents, divergent as regards certain characters, 
separating out in the germ cells of the offspring, without having had any 
influence on each other.” Then we read of “similar allelomorphs” uniting 
to form ‘“‘true-breeding, or homozygous individuals,’ and “dissimilar 
allelomorphs ” yielding ‘‘hybrids, or heterozygous individuals.” The 
different constituents of the latter are said to separate out again at some 
particular time, an exact knowledge of which is of ‘“‘enormous importance, 
both from the theoretical and practical stand-point.” It also seems 
necessary to distinguish the ‘‘ fundamental make up of a plant’’ before 
“‘ rapidly effecting desirable combinations of unit characters.” We have 
had to condense the enquiry, but the essential point is, how many of these 
alternating units does each reproductive cell contain? and what happens 
when they fail to alternate ? 
To begin at the beginning, what is known as Mendelism is a by-product 
of hybridisation. Its phenomena were discovered accidentally about the 
end of the eighteenth century, by Knight, when experimenting in the 
improvement of garden peas. Some twenty years later the same 
phenomena among garden peas were observed independently by Goss and 
Seton. These phenomena (explained at pp. 134-136), attracted the 
attention of the German experimenter, Gartner, who was familiar with the 
phenomena of hybridisation in other groups, and their abnormal character 
induced him also to conduct a series of experiments with peas, which 
confirmed the earlier observations. By the middle of the nineteenth century 
a mass of evidence on hybridisation generally had accumulated, and this led 
Mendel to search for some underlying principle governing the production 
of hybrids. By some unexplained coincidence he also chose garden peas for 
a series of experiments, the results of which he published in an elaborate 
paper in 1866. Mendel was apparently unaware of the work of his’ 
predecessors in this group, and spoke of the necessity of confirmation of the 
. 
