Fragments of wood not infrequently occur, with the tissues well-preserved by impregnation with the resin; while leaves, flowers and fruits are occasionally found in marvellous perfection.
Cell-walls may become modified by the impregnation of various substances.
Cross fertilization, or the impregnation of any given flower by pollen from another flower of the same species on the same or on another plant, has been proved to be of great - g advantage to the plant by securing a more FIG.
Improved varieties, obtained by cross-impregnation either naturally or artificially brought about, were carefully propagated and generally adopted, and increased attention was bestowed on the cultivation of the natural grasses.
As the ova are in many species deposited in a gelatinous tube secreted by the bodywalls, in which they are arranged (three or more together) in flaskshaped cavities, impregnation must probably take place either before or at the very moment of their being deposited.
The conclusion at which he arrives is that the pollen is not in all flowering plants necessary for impregnation, for fertile seeds can be produced without its influence.
They pair on land, the male clasping the female at the arms, and the impregnation is internal.
The females habitually produce eggs without impregnation, which again habitually develop into females, more rarely into males.
There is some reason to believe that this complicated and variable apparatus is used for stabbing the body of another animal and that beginning as a weapon for catching prey it has become modified for hypodermic impregnation and only gradually adapted for insertion into the bursa copulatrix.
They are particularly fond of salt, and in the Alps sandstone rocks containing a saline impregnation are often met with hollowed by the constant licking of these creatures.
After impregnation, the male twists them round his legs and returns to his usual retreat, going about at night in order to feed himself and to keep up the moisture of the eggs, even resorting to a short immersion in the water during exceptionally dry nights.
This remarkable double fertilization as it has been called, although only recently discovered, has been proved to take place in widely-separated families, and both in Monocotyledons and Dicotyledons, and there is every probability that, perhaps with variations, it is the normal process in Angiosperms. After impregnation the fertilized oosphere immediately surrounds itself with a cell-wall and becomes the oospore which by a process of growth forms the embryo of the new plant.
The oviducts may have diverticula serving as receptacles for the spermatozoa (in cases where internal impregnation takes place), and may be provided with glands secreting envelopes or shells around the eggs.