Nucellus

“ Gazette, xlvi., 1908, regards this tissue as belonging to the nucellus.) At the time of pollination the long tubular integument secretes a drop of fluid at its apex, which holds the pollen-grains, brought by the wind, or possibly to some extent by insect agency, and by evaporation these are drawn on to the top of the nucellus, where partial disorganization of the cells has given rise to an irregular pollen-chamber (fig. 17, A, pc) . The pollen-tube, containing two generative and one vegetative nucleus, pierces the wall of the megaspore and then becomes swollen (fig. 17, B and C, pt) ”

“ This is a large seed, with a very long micropyle; it has a beaked pollen-chamber, and a complex integument made up of hard and fleshy layers, closely resembling the seed of a modern Cycad; the nucellus, however, was free from the integument, each having its own vascular system. Various other seeds of the same type are known, and in a great number of instances Grand' Eury has found the fronds of Neuropterideae (Medulloseae) in close association with definite species of seeds, so there can be little doubt that the whole family was seed-bearing. Very little is known at present of the male organs. ”

“ When the pistil has reached a certain stage in growth it becomes ready for fertilization. Pollination having been effected, and the pollen-grain having reached the stigma in angiosperms, or the summit of the nucellus in gymnosperms, it is detained there, and the viscid secretion from the Fertilization. glands of the stigma in the former case, or from the nucellus in the latter, induce the protrusion of the intine as a pollen-tube through the pores of the grain. ”

“ The nucleolus is a small globular or oval particle, which may be found singly or in numbers in the nucleus, and behaves somewhat differently towards coloring matter [141] than the closely related chromatin. It has a special affinity for acid aniline colors, gosin, etc. Its substance has, therefore, been distinguished as plastin or paranuclein. The nucleolus is especially found in the tissue-cells of the higher animals and plants as an independent constituent; it is wanting in many of the unicellular protists. The same may be said of the centrosoma, or "central body" of the cell. ”

“ What has been said of the animal world is no less true of plants. Imbedded in the protoplasm at the broad, or attached, end of the nettle hair, there lies a spheroidal nucleus. Careful examination further proves that the whole substance of the nettle is made up of a repetition of such masses of nucleated protoplasm, each contained in a wooden case, which is modified in form, sometimes into a woody fibre, sometimes into a duct or spiral vessel, sometimes into a pollen grain, or an ovule. Traced back to its earliest state, the nettle arises as the man does, in a particle of nucleated protoplasm. ”

“ The nucleus in its turn, in completely developed cells, very constantly encloses another structure within itself—the so-called nucleolus. With regard to the question of vital form, it cannot be said of the nucleolus that it appears to be an absolute essential, and in a considerable number of young cells it has as yet escaped detection. On the other hand, we regularly meet with it in fully-developed, older forms, and it therefore seems to mark a higher degree of development in the cell. ”

“ Loc., fossil. In most of the British glacial beds, but not common.
Loc., living. Throughout the European Seas. Does not range to Greenland.
Note. It occurs in both coralline and red crags.
66. Nucula proxima, Gould?
Loc., fossil. Among the drift fossils collected by Captain James, in Wexford, is a Nucula, which comes nearer to the above species of Gould, as figured in the 'Invertebrata of Massachusetts' (fig. 63) , than to any species with which I am acquainted. The Nucula nitida of Sowerby may, as suggested by Dr. Gould, be the same species ”

“ Within the nucleus there was often a small dark spot or sphere—the nucleolus. The nucleus, Schleiden thought, originated as a minute granule in the cytoblastem which gradually increased in size, becoming first a nucleolus (Kernchen) , and then, by further condensation of matter round it, a nucleus. Several nuclei might be formed in this way in a single cell. New cells took their origin directly from a full-grown nucleus, in a peculiar way which Schleiden describes as follows:—"As soon as the cytoblasts have reached their full size a delicate transparent vesicle arises on their surface ”

“ Because in the reign of the heathen Emperor Julian, thou hast kept the word of my patience, I also will keep thee from the hour of temptation, which by the woman's flying into the wilderness, and the Dragon's making war with the remnant of her seed, and the killing of all who will not worship the Image of the Beast, shall come upon all the world, to try them that dwell upon the earth, and to distinguish them by sealing the one with the name of God in their foreheads, and marking the other with the mark of the Beast. Him that overcometh, I will make a pillar in the Temple of my God ”

“ The nucleus represents the most vital part of the cell protoplasm, and has a more granular appearance than the latter. The nucleolus is a minute solid spot in a nucleus, appearing to be more highly refractive. ”

“ If the spore mother cells are still quite young, we shall find the nucleus (Fig. 127, A, n) comparatively small, and presenting a granular appearance when strongly magnified. These granules, which appear isolated, are really parts of filaments or segments, which are closely twisted together, but scarcely visible in the resting nucleus. On one side of the nucleus may usually be seen a large nucleolus (called here, from its lateral position, paranucleus) , and the whole nucleus is sharply separated from the surrounding protoplasm by a thin but evident membrane. ”

“ If the ovule is from a flower that has been open for some time, we shall find in the centre of the embryo sac a large nucleus (k) (or possibly two which afterward unite into one) , and at each end three cells. Those at the base (g) probably represent the prothallium, and those at the upper end a very rudimentary archegonium, here generally called the “egg apparatus.” ”

“ And we have read in the writings of Numenius the Pythagorean regarding his formation, that he partakes of the essence of all the animals and plants that are under the control of nature, that he may appear to have been fashioned into a god, not by the makers of images alone, with the aid of profane mysteries, and juggling tricks employed to invoke demons, but also by magicians and sorcerers, and those demons who are bewitched by their incantations. ”

“ Hofmeister had observed the organisation of the ovule, the nature of the embryo-sac and of the pollen-grain, and the formation of the embryo from the fertilised egg-cell step by step and cell by cell, and his account of these processes was aided by the light which Nägeli's theory of the cell, and his reference of all processes of development to the processes of cell-formation, had thrown upon the history of development. ”

“ The question of the universal presence of nuclei in cells may be left open in the case of Plants, as in that of Animals; but, speaking generally, it may justly be affirmed that the nucleated cell is the morphological foundation of both divisions of the living world; and the great generalisation of Schleiden and Schwann, that there is a fundamental agreement in structure and {203} development between plants and animals, has, in substance, been merely confirmed and illustrated by the labours of the half century which has elapsed since its promulgation. ”

“ In cell-division the first stage is the aggregation, on opposite sides of the nucleus, in a line with the long axis of the cell, of a quantity of pale, slightly granular protoplasm. This is perhaps derived from the peripheral layer, and travels inward along the fibers, since minute thickenings, of similar appearance, show themselves upon these fibers. The nucleolus swells out into two protuberances, in the same axial line, joined by a bridge of denser matter. ”

“ Other as simple but larger organisms may consist of a minute mass of semi-fluid protoplasm, containing granules, as we find to be the case in the plant Vaucheria, [85] and many other Algæ, and in the animal Amœba primitiva. [86]
An organism of this simplest kind or a fragment of a higher organism which presents this simplest condition is called a cell. [87] Very generally [Pg 326] such cell has within it a more or less distinctly marked generally denser and spheroidal body called a nucleus, within which, again, other minute spots may appear called nucleoli. ”

“ The nucleus is generally rather more strongly compressed in the direction of the main axis than the capsule itself. The membrane of the vesicular nucleus is thin, but firm, and encloses a clear or finely granular mass of nuclein. The number and size of the contained nucleoli are variable even in one and the same species, and stand in inverse ratio to each other, an obvious result of the gradual process of division. Commonly {xl}from twenty to fifty roundish or spherical, strongly refracting nucleoli, are present; more rarely there are several hundred very small ones. ”

“ Soon after the new study of the nucleus began, investigators were struck by the fact that the course of nuclear division in the mother-cells, or more correctly in the grandmother-cells, of spores, pollen-grains, and embryo-sacs of the more highly organised plants and in the spermatozoids and eggs of the higher animals, exhibits similar phenomena, distinct from those which occur in the somatic cells. ”

“ Noetus, a Smyrnæan by birth, a reckless babbler and trickster, introduced this heresy, which originated with Epigonus, and was adopted by Cleomenes, and has thus continued to this day among his successors. Noetus asserts that there is one Father and God of the universe, and that He who had made all things was, when He wished, invisible to those who existed, and when He wished He became visible; that He is invisible when He is not seen and visible when He is seen; that the Father is unbegotten when He is not generated, but begotten when He is born of a virgin ”

“ This has an attractive influence on the fine granules or particles which are distributed in the protoplasm of the ovum; they arrange themselves in lines in the figure of a star. But the attraction or the “affinity” between the two nuclei is even stronger. They move towards each other inside the yelk with increasing speed, the male (Fig. 27 s k) going more quickly than the female nucleus (e k) . The tiny male nucleus takes with it the radiating mantle which spreads like a star about it. ”

“ Nuphar has 5 sepals, and an hypogynous flower. The petals, which are small, have a nectary on the back; the coloured inner side of the sepals functions as petals; the ovate gynœceum is quite free.—N. luteum is a native plant (Yellow Water-Lily) , with, most frequently, 13 petals and 10–16 loculi in the ovary. The rhizome is horizontal, as much as 5–6 cm. in thickness, and bears on its under surface a number of roots, which on dying-off leave deep scars; the leaves are borne in spiral lines, and the flowers are solitary in certain leaf-axils. ”

“ There is no special nucleolus. The rapid growth of the germinal epithelium is due [Pg 596] to the division of its cells, and great masses of these may frequently be seen to be undergoing division at the same time. Of the tissue of the ovary internal to the germinal epithelium, it may be noticed that the tubuliferous tissue derived from the Malpighian bodies is no longer in contact with the germinal epithelium, but that a layer of vascular stroma is to a great extent interposed between the two. The vascular stroma of the hilus has, moreover, greatly increased in quantity. ”

“ No man could turn him aside from the faith, nor by any means withdraw him from Julianus. Then was Martianus, and also Celsus' mother sorrowful in mind, and all their men; and Martianus asked the illustrious Julianus, ' Why wouldst thou destroy my only son by thy sorcery, and seduce him to thy Christ ? Behold our sorrow, and let our son go, and I will intercede for thee to our emperor.' Celsus, the son, said thus to the treacherous father, 'I renounce thee, father, for thy error, and I believe on Christ who hath chosen me. ”

“ The mode of origin of the nucleus and the part which it plays in the production of new cells have been the subject of much discussion. Schleiden, whose observations, published in 1838, were made on the cells of plants, believed that within the cell a nucleolus first appeared, and that around it molecules aggregated to form the nucleus. Schwann again, whose observations were mostly made on the cells of animals, considered that an amorphous material existed in organized bodies, which he called cytoblastema. ”

“ If the organic population of our planet has arisen naturally, and not by a miracle, as Reinke and other vitalists suppose, the earliest elementary organisms, produced by the chemical process of archigony (spontaneous generation) , could not be real nucleated cells, but unnucleated cytodes of the type of the chromacea [159] (cf. chapter ii.) . The nucleated real cell, as Oscar Hertwig and others define it to-day, can only have arisen by phylogenetic differentiation of nucleus and cell-body from the simple cytode of the monera. ”