BY GREGOR JOHN MENDEL
(Read at the Meetings of the 8th February and 8th March, 1865.)
Experience of artificial fertilization, such as is affected with ornamental plants in order to obtain new variations in color, has led to the experiments which will here be discussed. The striking regularity with which the same hybrid forms always reappeared whenever fertilization took place between the same species induced further experiments to be undertaken, the object of which was to follow up the developments of the hybrids in their progeny.
To this object numerous careful observers, such as Kolreuter, Gartner, Herbert, Lecoq, Wichura, and others, have devoted a part of their lives with inexhaustible perseverance. Gartner especially, in his work “Die Bastarderzeugung im Pflanzenreiche” (The Production of Hybrids in the Vegetable Kingdom), has recorded very valuable observations; and quite recently Wichura published the results of some profound investigations into the hybrids of the willow. That, so far, no generally applicable law governing the formation and development of hybrids has been successfully formulated can hardly be wondered at by anyone who is acquainted with the extent of the task and can appreciate the difficulties with which experiments of this class have to contend. A final decision can only be arrived at when we shall have before us the results of detailed experiments made on plants belonging to the most diverse orders.
Those who survey the work done in this department will arrive at the conviction that among all the numerous experiments made, not one has been carried out to such an extent and in such a way as to make 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.1
1 This translation was made by the Royal Horticultural Society of London, and is reprinted, by permission of the Council of the Society, with footnotes added and minor changes suggested by Professor W. Bateson, enclosed within [ ]. The original paper was published in the Verhandlungen naturforschender Verein in Brunn Abhandlungen, iv, 1865, which appeared in 1866.
It requires indeed some courage to undertake a labor of such far-reaching extent; this appears, however, to be the only right way by which we can finally reach the solution of a question the importance of which cannot be overestimated in connection with the history of the evolution of organic forms.
The paper now presented records the results of such a detailed experiment. This experiment was practically confined to a small plant group and is now, after eight years’ pursuit, concluded in all essentials. Whether the plan upon which separate experiments were conducted and carried out was the best suited to attain the desired end is left to the friendly decision of the reader.
SELECTION OF THE EXPERIMENTAL PLANTS
The value and utility of any experiment are determined by the fitness of the material to the purpose for which it is used, and thus in the case before us it cannot be immaterial what plants are subjected to experiment and in what manner such experiments are conducted.
The selection of the plant group which shall serve for experiments of this kind must be made with all possible care if it be desired to avoid from the outset every risk of questionable results.
The experimental plants must necessarily -
1. Possess constant differentiating characters.
2. The hybrids of such plants must, during the flowering period, be protected from the influence of all foreign pollen or be easily capable of such protection.
The hybrids and their offspring should suffer no marked disturbance in their fertility in the successive generations.
1 [It is to the clear...