_Dissemination._

Dissemination is effected by the agency of water, of air, of
animals--and fruits and seeds are therefore grouped in respect of this
as hydrophilous, anemophilous and zooidiophilous. The needs for these
are obvious--buoyancy in water and resistance to wetting for the
first, some form of parachute for the second, and some attaching
mechanism or attractive structure for the third. The methods in which
these are provided are of infinite variety, and any and every part of
the flower and of the inflorescence may be called into requisition to
supply the adaptation (see FRUIT). Special outgrowths, arils, of the
seed-coat are of frequent occurrence. In the feature of fruit and
seed, by which the distribution of Angiosperms is effected, we have a
distinctive character of the class. In Gymnosperms we have seeds, and
the carpels may become modified and close around these, as in _Pinus_,
during the process of ripening to form an imitation of a box-like
fruit which subsequently opening allows the seeds to escape; but
there is never in them the closed ovary investing from the outset the
ovules, and ultimately forming the ground-work of the fruit.


_Germination of Seed._

Their fortuitous dissemination does not always bring seeds upon a
suitable nidus for germination, the primary essential of which is a
sufficiency of moisture, and the duration of vitality of the embryo is
a point of interest. Some seeds retain vitality for a period of many
years, though there is no warrant for the popular notion that genuine
"mummy wheat" will germinate; on the other hand some seeds lose