Staining 15 CHAPTER I. Microsporogenesis. The microsporangium. The wall of the pollen-sac 17 The primitive archesporium 18 Tetrad-division. The definitive archesporium 20 The first nuclear division of the microspore-mother-cell 21 The second mitosis of the mother-cell 30 The problem of reduction 31 Development of the microspore.
With Plates XXIU, XXIV, and XXV. D URING the course of the present studies, the development of the archegonium and fertilization, together with the phenomena immediately preceding and following fecundation, were first carefully worked out in Pinus Strobus. Later, a far less extended study was made of Pinus austriaca, P. rigida, P. resinosa, and P. montana, var. uncinata. A complete series of stages in the development of these species was not obtained, and, therefore, the conclusions as set forth in this paper refer, unless otherwise stated, to Pinus Strobus, the other species being used only by way of .comparison. The methods employed in the preparation of the material for this research were fully described in my earlier paper ('01) and need not be repeated here. These investigations were begun, at the suggestion of Pro?. George F. Atkinson,.in the fall of 1897, and the principal results of the work, as herein described, were read before the Botanical Society of America at its Boston meeting in 1898. At this time Blackman's ('98) excellent article, ' Fertilization and Related Phenomena in Pinus sylvestris,' had
With Plates XII, "gTTT and XIV. INTRODUCTORY. '"T^HERE is perhaps no phase of botanical science to which-I-greater interest attaches at the present day than that which is concerned with the problems of sexual reproduction. The early botanists found in this question merely a favourite subject for philosophical speculation. Although Amici ('30-'46) made certain interesting observations regarding the development of the pollen-tube and the origin of the embryo in several plants, yet Hofmeister ('46-'62), whose works have already become classic, will ever be recognized as the first true scientific investigator along the line of sexual reproduction in plants. Since his studies, many botanists have found in this subject an attractive field for investigation. The celebrated discoveries of Ikeno, Hirase, and Webber, in 1897,gave a new incentive to this study, particularly in connexion with 1 Read before the Botanical Society of America at its sixth annual meeting in New York City, June 28, 1900.
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