THE ANNALS MAGAZINE OF NATURAL HISTORY. [THIRD SERIES.] No. 69. SEPTEMBER 1863. XV. — On the Impregnation in Orchids as a Proof of the two different Effects of the Pollen, By Dr. F. Hildebrand, of Bonn. Op late years most of the investigations on impregnation in plants have been directed to the pollen-tubes acting on the ovules to form the embryo. That there are a great many other interesting and important points respecting the fecundation of plants, everybody will admit who has directed attention to the two celebrated works of Darwin, ' On the Origin of Species ' and ' On the Fertilization of Orchids/ bearing in mind at the same time the inquiries of Koelreuter, Sprengel, Gaertner, Herbert, &c. Looking at some tropical Orchids cultivated in the Botanical Garden of Bonn, I found no ovules in the ovarium of the ex-panded flower ; nevertheless I saw the enlargement of the ova-rium after having applied the pollen to the stigma. This curious circumstance seemed deserving of further examination, especially as the numerous writers on the impregnation in Orchids* have made out this point imperfectly; and even Robert Brown, in his paper on the Fecundation in Asclepiadese and Orchidesef, has merely alluded to it. As my investigations are to be published at greater length in Mohl and SchlechtendaFs ' Botanische Zeitung,^ I shall describe only the experiments and observations made on one species, and then give the results of these and all the other experiments. The ovarium of Dendrobium nobile has a diameter of about * Brongniart in Ann. des Sc. Nat. 1831, p. 117; Amici, Flora, 1847, p. 255; Mohl, Bot. Zeitung, 1847, p. 465; HofFmeister, Entw. d. Embryo der Phanerog. p. 5; Schacht, Ann. des Sc. Nat. 1851, p. 83; Henfrey, Trans. Linn. Soc. xxi. p. 7-t Trans. Linn. Soc. 1833. Ann. ^ Mag. N. Hist. Ser. 3. Vol.xii. 12
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