selected in both experiments for fertilisation there agreed, as the following year’s culture showed, with the pollen parent:-- 1st Experiment. 2nd Experiment. 2 plants -- in all characters 3 " -- " 4 " -- 2 plants " 3 " -- 2 " " 2 " -- 1 plant " 1 character In the first experiment, therefore, the transformation was completed; in the second, which was not continued further, two more fertilisations would probably have been required. Although the case may not frequently occur that the dominant characters belong exclusively to one or the other of the original parent plants, it will always make a difference which of the two possesses the majority. If the pollen parent shows the majority, then the selection of forms for further crossing will afford a less degree of security than in the reverse case, which must imply a delay in the period of transformation, provided that the experiment is only considered as completed when a form is arrived at which not only exactly resembles the pollen plant in form, but also remains as constant in its progeny. Gärtner, by the results of these transformation experiments, was led to oppose the opinion of those naturalists who dispute the stability of plant species and believe in a continuous evolution of vegetation. He perceives in the complete transformation of one species into another an indubitable proof that species are fixed within limits beyond which they cannot change. Although this opinion cannot be unconditionally accepted we find on the other hand in Gärtner’s experiments a noteworthy confirmation of that supposition regarding variability of cultivated plants which has already been expressed. Among the experimental species there were cultivated plants, such as _Aquilegia atropurpurea_ and _canadensis_, _Dianthus caryophyllus_, _chinensis_, and _japonicus_, _Nicotiana rustica_ and _paniculata_, and hybrids between these species lost none of their stability after four or five generations[49]. [49] [The argument of these two last paragraphs appears to be that though the general mutability of natural species might be doubtful, yet among cultivated plants the transference of characters may be accomplished, and may occur by integral steps until one species is definitely “transformed” into the other.] ON HIERACIUM-HYBRIDS OBTAINED BY ARTIFICIAL FERTILISATION By G. Mendel. (_Communicated to the Meeting 9 June, 1869[50]._) [50] [Published in _Verh. naturf. Ver. Brünn, Abhandlungen_, VIII. 1869, p. 26, which appeared in 1870.] Although I have already undertaken many experiments in fertilisation between species of _Hieracium_, I have only succeeded in obtaining the following 6 hybrids, and only from one to three specimens of them.