Word Finder - hilum

definition

The eye of a bean or other seed; the mark or scar at the point of attachment of an ovule or seed to its base or support.

definition

The nucleus of a starch grain.

definition

A depression or fissure through which ducts, nerves, or blood vessels enter and leave a gland or organ; a porta.

Starch exists, in the majority of cases, in the form of grains, which are composed of stratified layers arranged around a nucleus or hilum.

This fissure represents the hilum of the liver, and contains the right and left hepatic ducts and the right and left branches of the hepatic artery and portal vein, together with nerves and lymphatics, the whole being enclosed in some condensed subperitoneal tissue known as Glisson's capsule.

The order is divided into five tribes by characters based on differences in position of the ovules - which are generally semianatropous so that the seed is peltate with the hilum in the centre on one side (or ventral), but sometimes, as in Hottonia and (From Strasburger's Lehrbuch der Botanik.) FIG.

On the other, posterior, side of the grain is a more or less evident, sometimes punctiform, sometimes elongated or linear mark, the hilum, the place where the ovule was fastened to the wall of the ovary.

The form of the hilum is constant throughout a genus, and sometimes also in whole tribes.

Hilum a point; spikelets not laterally compressed.

Hilum a line; spikelets laterally compressed.

The part by which the ovule is attached to the placenta or cord is its base or hilum, the opposite extremity being its apex.

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.

Sometimes 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 horizontal.

X-ray showed slight pulsation of the smooth round lesion above the left hilum.

When formed inside it, the starch-grains exhibit a concentric stratification; when formed externally in the outer layers, the stratification is excentric, and the hilum occurs on that side farthest removed from the leucoplast.

The outer layers are denser than the inner, the density decreasing more or less uniformly from the outside layers to the centre of hilum.

No characters for main divisions can be obtained from the flower proper or fruit (with the exception of the character of the hilum), and it has therefore been found necessary to trust to characters derived from the usually less important inflorescence and bracts.