Page:Popular Science Monthly Volume 77.djvu/357

Rh There is another case of a different kind. Sometimes the hybrid character is different from the character of the parents, even though the exact parental characters are reproduced by segregation in succeeding generations. The commercial carnation form is the result of crossing the single carnation with the huge worthless doubles called "busters." Reproduced by seed the commercial carnation throws both singles and busters, showing that segregation of the parental characters takes place; but as these plants are easily reproduced by cuttings, and the cuttings are all of the commercial type, sexual reproduction is only resorted to for the sake of producing new varieties. Another common phenomenon attending hybridization is sterility. Many very beautiful flowers produce no seed at all. This is even an advantage in some cases, because the plants flower more profusely than if they were spending their energies in the production of seed. Here again, cuttings are resorted to to reproduce the hybrid, or, as in the case of seedless oranges, the cuttings are grafted into an older rootstock instead of being rooted.

I stated at the beginning that there were two other classes of hybridization phenomena, the production of fixed first-generation hybrids and the production of blend hybrids. It is probable in the last analysis that the true explanation of these cases is the same; so we will consider them together. It is believed by many that there are kinds of inheritance other than Mendelian, that is, inheritance where no segregation occurs. Far be it from me to deny this; I simply state the fact that there are no exact data extant proving other kinds of inheritance. Such data may be found, but it is useless to speculate upon other laws without such evidence. There are several cases in which either new characters that breed true or blended characters that breed true appear to have been formed, but they have not been studied with sufficient care for an analysis of their mode of inheritance to be accurate and final. It is in crosses between true species that hybrids have been formed seemingly as constant and uniform as their parent species. Janczewsky has produced several such hybrids. Perhaps the most famous, however, are the blackberry-raspberry crosses first produced by the late E. S. Carman, editor of the Rural New-Yorker and later by Luther Burbank and others. Several hybrids having a commercial value have been made in this genus (Rubus), and all of them reproduce approximately true from seed. These are the facts and show what may sometimes be expected by hybridizers when crossing true species; but I wish to point out that this does not necessarily mean that we are dealing with a new mode of inheritance. Bramble species produce seedlings that are quite variable and in which the variations are extremely difficult to describe; there is, therefore, no exact information as to the relative variability of the hybrid seedlings as compared to that of the two parents. It may be said, then, that it is yet unknown whether there is partial segregation.