Un corso pratico in botanica : con particolare riferimento ai suoi cuscinetti sull'agricoltura, l'economia, e i servizi igienici . s troviamo nei boschi d'autunno sembrano fare? Per rispondere a questa domanda, esaminare i frutti commestibili del vostro quartiere e si willfind che quasi senza eccezione i semi sono duri e ossei, e o toospiccolo per essere cacciatoredby masticare, e thusable di passingunlured attraverso il sistema digestivo di un animale; o, iftoo grande per essere swal-lowed intero, com-odorare l'animale, dalla loro durezza sapore ordispiacevole, per respingerli. Incases dove le piantine sono ed-ible ed attr

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A practical course in botany : with especial reference to its bearings on agriculture, economics, and sanitation . s we find inthe autumn woods seem to do? To answer this question, examine the edible fruits of your neighborhood and you willfind that almost without exception the seeds are hard and bony, and either toosmall to be destroyedby chewing, and thuscapable of passinguninjured throughthe digestive systemof an animal; or, iftoo large to be swal-lowed whole, com-pelling the animal, by their hardness ordisagreeable flavor, to reject them. Incases where the seedsthemselves are ed-ible and attractive, the fruits are usuallyarmed during thegrowing season withprotective coverings, like the bur of the chestnut and the astringent hulls of the hick-ory nut and walnut. The acidity or other disagreeable quali-ties of most unripe fruits serves a similar purpose, while theirgreen color, by making them inconspicuous among the foliageleaves, tends still further to insure them against molestation. 22. Voluntary agency. — The cultivated fruits and grainsowe their distribution and survival almost entirely to the. Figs. 40-42.—Adhesive fruits : 40, fruit of hounds-tongue; 41, akene of bur marigold; 42, fruit of burgrass (cenchrus). THE SEED 25 voluntary agency of man. Dispersal by this means, whetherintentional or accidental, is purely artificial, and except in thecase of a few annuals like horseweed, bitterweed, ragweed, goosefoot, and other field pests that have adjusted their sea-son of growth and flowering to the conditions of cultivation, is not correlated with any special modification of the plantsfor self-propagation. On the contrary, many of the mostwidely distributed weeds of cultivation, such as the ox-eyedaisy, the rib grass, mayweed and bitterweed, possess veryimperfect natural means of dispersal, and are largely depend-ent for their propagation on the involuntary agency of man.23. Use of the fruit in dispersal. — It will be seen from theforegoing observations that th

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• bookcentury1900
• bookdecade1910
• bookpublisher
• booksubjectplants