_H. Auricula_ ♀ × _H. aurantiacum_ ♂ _H. Auricula_ ♀ × _H. Pilosella_ ♂ _H. Auricula_ ♀ × _H. pratense_ ♂ _H. echioides_[51] ♀ × _H. aurantiacum_ ♂ _H. præaltum_ ♀ × _H. flagellare_ Rchb. ♂ _H. præaltum_ ♀ × _H. aurantiacum_ ♂ [51] The plant used in this experiment is not exactly the typical _H. echioides_. It appears to belong to the series transitional to _H. præaltum_, but approaches more nearly to _H. echioides_ and for this reason was reckoned as belonging to the latter. The difficulty of obtaining a larger number of hybrids is due to the minuteness of the flowers and their peculiar structure. On account of this circumstance it was seldom possible to remove the anthers from the flowers chosen for fertilisation without either letting pollen get on to the stigma or injuring the pistil so that it withered away. As is well known, the anthers are united to form a tube, which closely embraces the pistil. As soon as the flower opens, the stigma, already covered with pollen, protrudes. In order to prevent self-fertilisation the anther-tube must be taken out before the flower opens, and for this purpose the bud must be slit up with a fine needle. If this operation is attempted at a time when the pollen is mature, which is the case two or three days before the flower opens, it is seldom possible to prevent self-fertilisation; for with every care it is not easily possible to prevent a few pollen grains getting scattered and communicated to the stigma. No better result has been obtained hitherto by removing the anthers at an earlier stage of development. Before the approach of maturity the tender pistil and stigma are exceedingly sensitive to injury, and even if they are not actually injured, they generally wither and dry up after a little time if deprived of their protecting investments. I hope to obviate this last misfortune by placing the plants after the operation for two or three days in the damp atmosphere of a greenhouse. An experiment lately made with _H. Auricula_ treated in this way gave a good result. To indicate the object with which these fertilisation experiments were undertaken, I venture to make some preliminary remarks respecting the genus _Hieracium_. This genus possesses such an extraordinary profusion of distinct forms that no other genus of plants can compare with it. Some of these forms are distinguished by special peculiarities and may be taken as type-forms of species, while all the rest represent intermediate and transitional forms by which the type-forms are connected together. The difficulty in the separation and delimitation of these forms has demanded the close attention of the experts. Regarding no other genus has so much been written or have so many and such fierce controversies arisen, without as yet coming to a definite conclusion. It is obvious that no general understanding can be arrived at, so long as the value and significance of the intermediate and transitional forms is unknown.