. British piante; la loro biologia ed ecologia. La botanica; botanica; Ecologia vegetale. Frutti e semi 197 stroyed, ma alcuni sono portati via e lasciato cadere, altri conservati nei fori e dimenticato. (6) collante i frutti e le sementi diventano attaccato al hairy cappotti degli animali e possono essere trasportate per distanze considerevoli prima che essi sono infine lasciato cadere o sfregamento. In bardana il achenes sono lisce ma le brattee involucral racchiudente la testa sono agganciati; i frutti di cleavers [Galium aparine) e incantatore - nightshade (Circcea lutetiana) sono coperti con brevi setole rigide ; il achenes di avens (Geum) ar

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. British plants; their biology and ecology. Botany; Botany; Plant ecology. FRUITS AND SEEDS 197 stroyed, but some are carried away and dropped, others stored in holes and forgotten. (6) Adhesive fruits and seeds become attached to the hairy coats of animals, and may be carried considerable distances before they are finally dropped or rubbed off. In burdock the achenes are smooth, but the involucral bracts enclosing the head are hooked; the fruits of cleavers [Galium Aparine) and enchanter's - nightshade (Circcea lutetiana) are covered with short stiff bristles ; the achenes of avens (Geum) are hooked (Fig. 106). In Bidens (the bur-marigold), the achenes are armed with barbed prongs (Fig. 107) ; in agrimony the receptacle is covered on the outside with hooked bristles. 5. Water-Borne Fruits and Seeds.—Aquatics which flower and fruit under water must obviously have their. Fig. ]05.—Dehisced Fig. 106.—Achene or Fig. 107. — Acbene Capsule OP Violet. AvEKs(G'e«m), with (Cypsela) of Bur- Hooked Style. Makigold (Bidena). seeds dispersed by water. Seeds dropped into water may float and be carried some distance and washed up on land. Dry fruits often contain a considerable amount of enclosed air. If such fruits fall into water, they float and may be driven along the surface of the water by the wind. In this case the agent of distribution is the wind, not the water. Few special structures for water-dispersal are found among English fruits. In the white water-lilj^ however, the fruit is a large berry, containing a large number of seeds. Each seed is surrounded by a spongy aril, containing cavities filled with air. When the fruit opens, the seeds float up to the surface of the water, and are drifted about until the aril rots, when they sink. In fresh water seeds may germinate while floating on the surface—e.g., wUlowherb. If driven ashore by the wind, they may continue to live.. Please note that these images are extracted from scanned page images that may have been

Parole chiave associate all'immagine

• bookcentury1900
• bookdecade1920
• booksubjectbotany
• bookyear1920