14 PRESIDENT’S ADDRESS, 
new varieties of cultivated plants are the outcome of deliberate crossing. 
There is generally no doubt in the matter. We have pretty full 
histories of these crosses in Gladiolus, Orchids, Cineraria, Begonia, 
Calceolaria, Pelargonium, &. A very few certainly arise from a single 
origin. The Sweet Pea is the clearest case, and there are others which 
I should name with hesitation. The Cyclamen is one of them, but 
we know that efforts to cross Cyclamens were made early in the cul- 
tural history of the plant, and they may very well have been success- 
ful. Several plants for which single origins are alleged, such as the 
Chinese Primrose, the Dahlia, and Tobacco, came to us in an already 
domesticated state, and their origins remain altogether mysterious. 
Formerly single origins were generally presumed, but at the present 
time numbers of the chief products of domestication, dogs, horses, 
cattle, sheep, poultry, wheat, oats, rice, plums, cherries, have in turn 
been accepted as ‘ polyphyletic,’ or, in other words, derived from several 
distinct forms. The reason that has led to these judgments is that the 
distinctions between the chief varieties can be traced as far back as the 
evidence reaches, and that these distinctions are so great, so far tran- 
scending anything that we actually know variation capable of effecting, 
that it seems pleasanter to postpone the difficulty, relegating the critical 
differentiation to some misty antiquity into which we shall not be asked 
to penetrate. For it need scarcely be said that this is mere procrastina- 
tion. If the origin of a form under domestication is hard to imagine, it 
becomes no easier to conceive of such enormous deviations from type 
coming to pass in the wild state. Examine any two thoroughly distinct 
species which meet each other in their distribution, as, for instance, 
Lychnis diurna and vespertina do. In areas of overlap are many inter- 
mediate forms. ‘These used to be taken to be transitional steps, and 
the specific distinctness of vespertina and diurna was on that account 
questioned. Once it is known that these supposed intergrades are 
merely mongrels between the two species the transition from one to the 
other is practically beyond our powers of imagination to conceive. If 
both these can survive, why has their common parent perished? Why 
when they cross do they not reconstruct it instead of producing partially 
sterile hybrids? I take this example to show how entirely the facts 
were formerly misinterpreted. 
When once the idea of a true-breeding—or, as we say, homozygous 
—type is grasped, the problem of variation becomes an insistent oppres- 
sion. What can make such a type vary? We know, of course, one 
way by which novelty can be introduced—by crossing. Cross two 
well-marked varieties—for instance, of Chinese Primula—each breeding 
true, and in the second generation by mere recombination of the various 
factors which the two parental types severally introduced, there will 
be a profusion of forms, utterly unlike each other, distinct also from 
