And this demonstration has been completed by the final establishment of the cell theory (see Cytology), which involves the admission of a primitive conformity, not only of all the elementary structures in animals and plants respectively, but of those in the one of these great divisions of living things with those in the other.
For a more detailed description of the cell see CYTOLOGY and the section on Cytology of Plants below).
Consist of woody substance) and are irregularly but thickly studded with simple pits (see CYTOLOGY), which are usually arranged in spirals running round the cells, and are often elongated in the direction of the spiral (fig.
CYTOLOGY OF PLANTS
Upon our knowledge of its minute structure or cytology, combined with a study of its physiological activities, depends the ultimate solution of all the important problems of nutrition.
Xxi.; Blackman, On the Fertilization, Alternation of Generations, and General Cytology of the Uredineae, Ann.
(bot.): (1888); Delage, LAnnee biologique: confptes rendus annuels des travaux de biologic gnrale (Paris, 1895), &c.; Farmer, Recent Advances in Vegetable Cytology, Science Progress (1896), vol.
Thus Bionomics is treated in such articles as Evolution, Heredity, Variation, Mendelism, Reproduction, Sex, &C.; Zoo-dynamics under Medicine, Surgery, Physiology, Anatomy, Embryology, and allied articles; Plasmology under Cytology, Protoplasm, &C.; and Philosophical Zoology under numerous headings, Evolution, Biology, &C. See also Zoological Distribution, Palaeontology, Ocranography, Microtomy, &C.
But practical necessity has given rise to the existence of many other divisions; see CYTOLOGY, for the structure of cells; EMBRYOLOGY, for the development of individual organisms; HEREDITY and REPRODUCTION, for the relations between parents and offspring.
Normal cytology, of late, has become a science of itself, and has had a direct bearing upon that which is pathological.
The cytology of bone marrow, with the technique of blood examination, is of great assistance in the diagnosis of different pathological conditions.
Until the discovery of protoplasm, and the series of investigations by which it was established that the cell was a fundamental structure essentially alike in both animals and plants (see Cytology), there was a vague belief that plants, if they could really be regarded as animated creatures, exhibited at the most a lower grade of life.
De Bary and others, while more recently, as cytology (q.v.), the intimate study of the cell and its contents has attracted considerable attention.
Cytology (q.v.), the intimate structure and behaviour of the cell and its contents - protoplasm, nucleus, &c.
The general relation between parent and filial organisms is discussed under Heredity and Embryology; many of the details of the cellular processes are dealt with under Cytology, and the modes of reproduction exhibited by different kinds of animals and plants are treated of in the various articles describing individual groups.
- MOSt of the recent work of importance in this group deals with the cytology of sexual reproduction and of spore-formation, and the effect of external conditions on the production of reproductive organs.
The cytology of zygospore-formation is not known in detail; the so-called gametes which fuse are multinucleate and are no doubt of the nature of gametangia.
The cytology of these forms is very little known; Dangeard states that there is a fusion of two nuclei in the chlamydospore, but this requires confirmation.
(1905); Klebahn, Die wirtwechselnden Rostpilze (Berlin, 1904); Sapin-Trouffy, "Recherches histologiques sur la famine des Uredinees," Le Botaniste (1896-1897); Blackman, "On the Fertilization, Alternation of Generations and General Cytology of the Uredineae," Ann.
The number of chromosomes (see Plants: Cytology) in the nucleus of the two spores, pollen-grain and embryo-sac, is only half the number found in an ordinary vegetative nucleus; and this reduced number persists in the cells derived from them.
The results of future research on the cytology of the group will be awaited with interest.
Williams, " Contributions to our Knowledge of the Lifehistory and Cytology of Fucaceae," Phil.