The viscid pulp soon hardens, affording a protection to the seed; in germination the sucker-root penetrates the bark, and a connexion is established with the vascular tissue of the first plant.
A totally reflecting prism placed inside the glass cylinder projects the light which penetrates the film upon a selenium cell situated at the end of the cylinder.
(After Kleinenberg, from Gegenbaur.) access of water to the contents; when the cnidocil is stimulated it sets in action a mechanism or perhaps a series of chemical changes by which the plug is dissolved or removed; as a result water penetrates into the capsule and causes its contents to swell, with the result that the thread is everted violently.
The sharp, broken end penetrates the skin, and into the slight wound thus formed the formic acid contained by the hair is injected.
In many Gymnosperms the male nucleus penetrates the female nucleus before fusing with it (Blackman, Ikeno).