Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/92

82 the wild flowers, which, by entering the female flowers, caused them to set and ripen. The process was called palinification. Theophrastus, who succeeded Aristotle in his school in the 114th Olympiad, frequently mentions the sexes of plants, but he does not appear to have determined the organs of reproduction. Pliny, who flourished under Vespasian, speaks particularly of a male and female Palm, but his statements were not founded on any real knowledge of the organs. From Theophrastus down to Ctesalpinus, who died at Rome in 1G03, there does not appear to have been any attention paid to the reproductive organs of plants. Coosalpinus had his attention directed to the subject, and he speaks of a halitus or emanation from the male plants causing fertility in the female. Grew seems to have been the first to describe, in a paper on the Anatomy of Plants, read before the Royal Society in November 1G7G, the functions of the stamens and pistils. Up to this period all was vague conjecture. Grew speaks of the attire, or the stamens, as being the male parts, and refers to conversations with Sir Thomas Millington, Savilian professor at Oxford, to whom the credit of the sexual theory seems really to belong. Grew says that, &quot; when the attire or apices break or open, the globules or dust falls down on the seedcasc or uterus, and touches it with a prolific virtue.&quot; Ray adopted Grev/ s views, and states various arguments to prove their correctness in the preface to his work on European plants, published in 1G94. In 1694 Carnerarius, professor of botany and medicine at Tubingen, published a letter on the sexes of plants, in which he refers to the stamens and pistils as the organs of repro duction, and states the difficulties he had encountered in determining the organs of Cryptogamic plants. In 1703 Samuel Morland, in a paper read before the Royal Society, stated that the farina (pollen) is a congeries of seminal plants, one of which must be conveyed into every ovum or seed before it can become prolific. In this remarkable state ment he seems to anticipate in part the discoveries after wards made as to pollen tubes, and more particularly the peculiar views promulgated by Schleiden. In 1711 Geoffroy, in a memoir presented to the Royal Academy at Paris, sup ported the views of Grew and others as to the sexes of plants. He states that the germ is never to be seen in the seed till the apices (anthers) shed their dust; and that if the stamina be cut out before the apices open, the seed will either not ripen, or be barren if it ripens. He mentions two experiments made by him to prove this one by cut ting off the staminal flowers in Maize, and the other by rearing the female plant of Mercurialis apart from the male. In these instances most of the flowers were abortive, but a few were fertile, which he attributes to the dust of the apices having been wafted by the wind from other plants. Linnaeus was the next botanical author who took up the subject, and by his sexual system he may be said to have opened a new era in the history of botany. He first published his views in 173G, and he thus writes &quot;Antheras et stigmata constituere sexum plantarum, a palmicolis, Mill- ingtouo, Grewio, Rayo, Camerario, Godofrcdo, Moiiando, Vaillantio. Blairio, Jussievio, Bradleyo, Royeno, Logano, &c., detectum, descriptum, et pro infallibili assumptum ; nee ullum, apertis oculis considerantem cujuscunque plant.-B flores, latere potest.&quot; He divided plants into sexual and asexual, the former being Phanerogamous or flowering, and the latter Cryptogamoas or flowerless. In the latter divi sion of plants he could not detect stamens and pistils, and he did not investigate the mode in which their germs were produced. He was no physiologist, and did not promulgate any views as to the embryogcnic process. His followers were chiefly engaged in the arrangement and classification of plants, and while descriptive botany made great advances, the physiological department of the science was neglected. His views were not, however, adopted at once by all, for we find Alston stating arguments against them in his Disser tation on the Sexes of Plants. Alston s observations were founded on what occurred in certain unisexual plants, such as Mercurialis, Spinach, Hemp, Hop, and Bryony. The conclusions at which he arrives arc those of Pontedera, that the pollen is not in all flowering plants necessary for impregnation, for that fertile seeds can be produced with out its influence. He supports parthenogenesis in some plants. Soon after the promulgation of Linnseus s method of classification, the attention of botanists was directed to the study of Cryptogamic plants, and the valuable work of Hedwig on the reproductive organs of Mosses made its appearance in 1782. lie was one of the first to point out the existence of certain cellular bodies in these plants which appeared to perform the functions of reproductive organs, and to them the name of antheridia and pistillidia were given. This opened up a new field of research, and led the way in the study of Cryptogamic reproduction, which has since been much advanced by the- labours of numerous botanical inquirers. The interesting observa tions of Morland, already quoted, seem to have been neglected, and no one attempted to follow in the path which he had pointed out. Botanists were for a long time content to know that the scattering of the pollen from the anther, and its application to the stigma, were necessary for the production of perfect seed, but the stages of the process of fertilization remained unexplored. The matter seamed involved in mystery, and no one attempted to raise the veil which hung over the subject of embryogeny. The general view was, that the embryo originated in the ovule, which was in some obscure manner fertilized by the pollen. In 1815 Trevirauus roused the attention of botanists to the development of the embryo, but although he made valuable researches, he did not add much in the way of new information. In 1823 Amici discovered the exist ence of pollen tubes, and he was followed by Brongniart and Brown. The latter traced the tubes as far as the nucleus of the ovule. These important discoveries mark a new epoch in embryology, and may be said to be the foundation of the views now entertained by physiologists, which have been materially aided by the subsequent eluci dation of the process of cytogenesis, or cell-development, by Schleiden, Schwann, Mohl, and others. The whole subject has been investigated recently with great assiduity and zeal by physiologists, as regards both Cryptogainous and Phanerogamous plants. The formation of germinal vesicles in the ovule, and the development of the embryo in flowering plants, have been fully considered by Griffith, Schleiden, Mirbcl, Spach, Meyen, Schacht, Mohl, linger, Naudin, Radlkofer, and others ; the embryogenic process in Coniferous plants and in the higher Cryptogams by Hof- meister, Henfrey, Suminski,Mettcnius, Strasburger, Eichler, Baillon, Cohn, Pringsheim, Millardet ; and that of the lower Cryptogams by Thurct, Bornet, Decaisne, and Tulasne. The observations of Darwin as to the fertilization of Orchids. Primula, Linum, and Lythrum, and the part which in sects take in this function, have opened up a new era in Physiological Botany. He has been followed by Hermann Miiller. Darwin s experiments in reference to the move ments of climbing and twining plants, and of leaves in insectivorous plants, have opened up a wide field of inquiry which he has cultivated with eminent success and with most important results. Among other authors who have contributed to the advance of Vegetable Physiology may be named Hoffmann, Sachs, Van Tieghcm, Prillieux, Dehc- rain, and Famintzen. We have thus been enabled to come to certain general conclusions on this obscure subject, and 