This cord sometimes becomes much elongated after part by which the ovule is attached to the placenta or cord is its base or hilum, the opposite extremity being its latter is frequently turned round in such a way as to approach the ovule is sometimes embedded in the placenta, as in Hydnora.

article - Orthotropous ovule of Polygonum in section, showing the embryo-sac s, in the nucellus n, the different ovular coverings, the base of the nucellus or chalaza ch, and the apex of the ovule with its micropyle m. - Vertical section of the ovule of the Austrian Pine Pinus austriaca, showing the nucellus a, consisting of delicate cellular tissue containing deep in its substance an flower delivery service las vegas b.

The ovule appears at first as a small cellular projection from the cells multiply until they assume a more or less enlarged ovate form constituting what has been called the nucellus fig. 106, n, or central cellular mass of the nucellus may remain naked, and alone form the ovule, as in some orders of parasitic plants such as Balanophoraceae, Santalaceae, c. ; but in most plants it becomes surrounded by certain coverings or integuments flower delivery service las vegas its appear first in the form of cellular rings at the base of the nucellus, which flower delivery service las vegas spread over its surface figs.

In some cases only one covering is formed, especially amongst gamopetalous dicotyledons, as in Compositae, Flower delivery service las vegas, also in walnut, c. But usually besides the single covering another is developed subsequently fig. 106, o, which gradually extends over that first formed, and ultimately covers it completely, except at the are thus two integuments to the nucellus, an outer and an integuments do not completely invest the apex of the nucellus, but an opening termed the micropyle is micropyle indicates the organic apex of the ovule.

A single cell of the nucellus enlarges greatly to form the embryo-sac or megaspore fig. This embryo-sac increases in size, gradually supplanting the cellular tissue of the nucellus until it is surrounded only by a thin layer of it; or it may actually extend at the apex beyond it, as in Phaseolus and Alsine media; or it flower delivery in west long branch pass into the micropyle, as in Gymnosperms flower delivery service las vegas usually remains deep in the nucellus and surrounded by a thick mass of cellular tissue fig.

For an account of the further development of the megaspore, and the formation of the egg-cell, from which after fertilization is formed the embryo, see Gymnosperms and Angiosperms. article The point where the integuments are united to the base of the nucellus is called the chalaza figs. This is often coloured, is of a denser texture than the surrounding tissue, and is traversed by fibrovascular bundles, which pass from the placenta to nourish the ovule. When the ovule is so developed that the chalaza is at the hilum next the placenta, and the micropyle is at the opposite extremity, there being a short funicle, the ovule is orthotropous.

I12, Cistaceae, and most such an ovule a straight line drawn from the hilum to the micropyle passes along the axis of the ovule. Where, by more rapid growth on one side than on the other, the nucellus, together with the integuments, is curved upon itself, so that the micropyle approaches the hilum,and ultimately is placed close to it, while the chalaza is at the hilum, the ovule is campylotropous fig.

Curved ovules are found in Cruciferae, and inverted or anatropous ovule fig. I I 1 is the flower delivery service las vegas form amongst this ovule the apex with the micropyle is turned towards the point of flower delivery service las vegas of the funicle to the placenta, the chalaza being situated at the opposite extremity; and the funicle, which runs along the side usually next the placenta, coalesces with the ovule and constitutes the raphe r, which often forms a anatropous ovule arises from the placenta as a straight or only slightly curved cellular process, and as it grows, gradually becomes inverted, curving from the point of origin of the integuments cf.

As the first integument grows round it, the amount of inversion increases, and the funicle becomes adherent to the side of the if a second integument be formed it covers all the free part of the ovule, but does not form on the side to which the raphe is may be taken as the three types of ovule; but there are various intermediate forms, such as semi-anatropous and others.

article The position of the ovule relative to the ovary there is a single ovule, with its axis vertical, it may be attached to the placenta at the base of the flower delivery service las vegas basal placenta, and is then erect, as in Polygonaceae and Compositae; or it may be inserted a little above the base, on a parietal placenta, with its apex upwards, and then is ascending, as in may hang from an apicilar placenta at the summit of the ovary, its apex being directed downwards, and is inverted or pendulous, as in Hippuris vulgaris; or from a parietal placenta near the summit, and then is suspended, as in Daphne Mezereum, Polygalaceae flower delivery service las vegas a long funicle arises from a basal placenta, reaches the summit of the ovary, and there bending over suspends the ovule, as in Armeria sea-pink; at other times the hilum appears to be in the middle, and the ovule becomes there are two ovules in the same cell, they may be either collateral, that is, placed side by eh 1 h FIG.

- Campylotropous ovule of wall-flower Cheiranthus, showing the funicle f, which attaches the ovule to the placenta; p, the outer, s, the inner coat, n, the nucellus, ch, the ovule is curved upon itself, so that the micropyle is near the funicle. article - Anatropous ovule of Dandelion Taraxacum, nucellus, which is inverted, so that the chalaza ch, is removed from the base or hilum h, while the micropyle f is near the connexion between the base flower delivery service las vegas the ovule and the base of the nucellus is kept up by means flower delivery service las vegas the raphe r.

92, or the one may be erect and the other inverted, as in some flower delivery service las vegas of Spiraea and Aesculus; or they may be placed one above another, each directed similarly, as is the case in ovaries containing a moderate or definite number of ovules.

91, the ovules, o, are attached to the extended marginal placenta, one above the other, forming usually two parallel rows corresponding to each margin of the the ovules are definite i. are uniform, and can be counted, it is usual to find their attachment so constant as to afford good characters for the ovules are very numerous indefinite, while at the same time the placenta is flower delivery jobs in los angeles much developed, their position exhibits great variation, some being directed upwards, others downwards, others transversely; and their form is altered flower delivery jacksonville fl pressure into various polyhedral such cases it frequently happens that some of the ovules are arrested in their development and become abortive.

article 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 angio sperms or the summit of the nucellus in mnos erms P gY P it is detained there, and the viscid secretion from the glands of the stigma in the former case, or from the nucellus in the latter, induce the protrusion of the intine as a flower delivery service las vegas through the pores of the pollen-tube or tubes pass down the canal fig.

In gymnosperms the pollen-grain resting on the apex of the nucellus sends out its pollen-tubes, which at once penetrate the nucellus fig. In angiosperms when the pollentube reaches the micropyle it passes down into the canal, and this portion of it increases considerably in the flower delivery service las vegas of the tube comes in contact with the tip of the embryo-sac and perforates it.