SPECIES HYBRIDIZATION 245 
bination of species within the genus, and also of the mutants of 0. 
lamarckiana with the parent species, with one another, and with other 
species. 
As an example of the type of behavior displayed by these hybrids we 
shall take the results of intercrossing lamarckiana and its two mutant 
derivatives rubrinervis and nanella. When lamarckiana is crossed with 
rubrinervis, the phenomena are as outlined below: 
lamarckiana X rubrinervis 
lamarckiana subrobusta 
lamarckiana subrobusta rubrinervis 
The F, consists of two forms in about equal proportions, lamarckiana 
and subrobusta, the latter a form intermediate between lamarckiana and 
rubrinervis. In subsequent generations, the lamarckiana individuals 
breed true, but the subrobusta individuals produce both subrobusta and 
rubrinervis, the latter breeding true. To these results we may add those 
obtained by crossing lamarckiana and nanella, the dwarf mutant of 
lamarckiana. This cross gives in Ff; approximately equal numbers of 
lamarckiana and nanella and both forms breed true in subsequent 
generations. Finally to complete the triangle we may consider the 
results of hybridization of rubrinervis and nanella which are given below 
in the form of a diagram. 
nanella * rubrinervis 
lamarckiana subrobusta 
lamarckiana rubrinervis subrobusta dwarfs 
The percentage of suwbrobusta individuals in the F; of this cross is usually 
considerably below 50 per cent. In subsequent generations the subro- 
busta individuals segregate in the same fashion as those of the ’;. The 
dwarfs obtained in this experiment unite the characters of rubrinervis 
and nanella and are consequently designated rubrinervis nanella to dis- 
tinguish them form the true nanella. Like the lamarckiana and rubri- 
nervis individuals, they breed true in subsequent generations. The actual 
results of this series of experiments are given in Table XX XIX, from 
which data on those forms which bred true is omitted. It is at once ap- 
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