Dispersal of tree seeds by water, as in the case of certain water plants, occurs less frequently. Of the European trees the older is one whose seeds are dispersed by water as well as by the wind, and of the tropical species the coconut palm is a noteworthy example.
The small seed of the alder is equipped with air sacs that keep it afloat on the water surface for weeks until the spring floods carry it far afield. The coconut palm, now mild on the shores of continents as well as tropical islands, was brought to these places by sea currents and the regular swell of the ocean. But over long distances man also played its part.
To ensure that they fall in a suitable open space and do not merely drop beside the parent tree, where the prospects for their further growth are poor, the seeds are adapted for dissemination to longer or shorter distances. Most are equipped for dispersal by the wind and are either covered with down (willow, poplar) or have membranous wings (birch, elm, pine, spruce) or thick wings (maple, lime, hornbeam). The seeds of another group of woody plants are dispersed by animals, mainly birds. In general these are trees with pulpy, bright coloured fruits which serve as food for the birds, the seeds then being disseminated over a wide area in their excrement (mountain ash, cherry, yew).
A third group is formed by seeds which are themselves food for birds and mammals (oak, beech, walnut) and even though most are eaten, some are way. One would think that seed dispersal by animals is less effect ive than by wind, but the history of tree migration in the wake if retreating ice sheet in the period following the Ice Age gives evidence to the contrary.
Birch and pine, the first pioneers, were followed by the rapid northward spread of the oak and hazel, whose heavy seeds fall only a few metres from the parent Fee. Acorns, however, are a favourite food of jays and pigeons, while hazelnuts are eaten by nutcrackers and woodpeckers and e sometimes carried great distances in their beaks.
Dry fruits with a dry and hard outer wall are Samara - usually a winged, one-seeded fruit with thin, membranous to leathery coat (birch, elm, ash); Nut - a one-seeded fruit with hard, woody wall not connected with the seed (hazel, lime, hornbeam); Legume - usually the product of two carpels splitting along two lines of suture when ripe and containing several seeds; characteristic of most members of the family Leguminosae; Capsule - a single or several valved fruit splitting in various ways when ripe and containing several seeds (poplar, willow, chestnut). Fleshy fruits have soft, fleshy walls; Drupe - usually a one-seeded fruit with a coat comprising three layers: a thin outer layer, middle fleshy layer and a hard bony layer - the stone encasing the seed (cherry, walnut); Berry - a fruit with thin membranous covering and fleshy centre with one or several seeds embedded in the pulpy mass; few trees bear true berries. - 16035
The small seed of the alder is equipped with air sacs that keep it afloat on the water surface for weeks until the spring floods carry it far afield. The coconut palm, now mild on the shores of continents as well as tropical islands, was brought to these places by sea currents and the regular swell of the ocean. But over long distances man also played its part.
To ensure that they fall in a suitable open space and do not merely drop beside the parent tree, where the prospects for their further growth are poor, the seeds are adapted for dissemination to longer or shorter distances. Most are equipped for dispersal by the wind and are either covered with down (willow, poplar) or have membranous wings (birch, elm, pine, spruce) or thick wings (maple, lime, hornbeam). The seeds of another group of woody plants are dispersed by animals, mainly birds. In general these are trees with pulpy, bright coloured fruits which serve as food for the birds, the seeds then being disseminated over a wide area in their excrement (mountain ash, cherry, yew).
A third group is formed by seeds which are themselves food for birds and mammals (oak, beech, walnut) and even though most are eaten, some are way. One would think that seed dispersal by animals is less effect ive than by wind, but the history of tree migration in the wake if retreating ice sheet in the period following the Ice Age gives evidence to the contrary.
Birch and pine, the first pioneers, were followed by the rapid northward spread of the oak and hazel, whose heavy seeds fall only a few metres from the parent Fee. Acorns, however, are a favourite food of jays and pigeons, while hazelnuts are eaten by nutcrackers and woodpeckers and e sometimes carried great distances in their beaks.
Dry fruits with a dry and hard outer wall are Samara - usually a winged, one-seeded fruit with thin, membranous to leathery coat (birch, elm, ash); Nut - a one-seeded fruit with hard, woody wall not connected with the seed (hazel, lime, hornbeam); Legume - usually the product of two carpels splitting along two lines of suture when ripe and containing several seeds; characteristic of most members of the family Leguminosae; Capsule - a single or several valved fruit splitting in various ways when ripe and containing several seeds (poplar, willow, chestnut). Fleshy fruits have soft, fleshy walls; Drupe - usually a one-seeded fruit with a coat comprising three layers: a thin outer layer, middle fleshy layer and a hard bony layer - the stone encasing the seed (cherry, walnut); Berry - a fruit with thin membranous covering and fleshy centre with one or several seeds embedded in the pulpy mass; few trees bear true berries. - 16035
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Garden planning design should be fairly detailed and specific and include an indication of the type of planting envisaged in the different garden beds.
