Elementary botany . Fig. of red oak. An acorn. carpels separate from each other, but do not themselves dehisceand free the seed, as in the carrot family, mallow family. 873. The acorn.—The acorn fruit consists of the acorn andthe cup at the base in which the acorn sits. The cup is acurious structure, and is supposed to be composed of an involucreof numerous small leaves at the base of the pistillate flower,which become consolidated into a hard cup-shaped body. Whenthe acorn is ripe it easily separates from the cup, but the hardpericarp forming the shell of the acorn remains closed. F
Elementary botany . Fig. of red oak. An acorn. carpels separate from each other, but do not themselves dehisceand free the seed, as in the carrot family, mallow family. 873. The acorn.—The acorn fruit consists of the acorn andthe cup at the base in which the acorn sits. The cup is acurious structure, and is supposed to be composed of an involucreof numerous small leaves at the base of the pistillate flower,which become consolidated into a hard cup-shaped body. Whenthe acorn is ripe it easily separates from the cup, but the hardpericarp forming the shell of the acorn remains closed. Frostmay cause it to crack, but very often the pericarp is split open atthe smaller end by wedge-like pressure exerted by the emergingradicle during germination. 452 RELATION TO ENVIRONMENT, 874. The hazelnut, chestnut, and beechnut.—In these fruits acrown of leaves (involucre) at the base of the flower grows around. Fig. 474-Germinating acorn of white oak. the nut and completely envelops it, forming the husk or the fruit is ripe the nut is easily shelled out from the the beechnut and chestnut the burr dehisces as it dries andallows the nut to drop out. But the fruit is not dehiscent, sincethe pericarp is still intact and encloses the seed. 875. The hickory-nut, walnut, and butternut.—In these fruitsthe shuck of the hickory-nut and the hull of the walnutand butternut are different from the involucre of the acorn orhazelnut, etc. In the hickory-nut the shuck probably con-sists partly of calyx and partly of involucral bracts consolidated,probably the calyx part predominating. This part of the fruitsplits open as it dries and frees the nut, the pericarp beingvery hard and indehiscent. In the walnut and butternut thehull is probably of like origin as the shuck of the hickorynut, but it does not split open as it ripens. It remains walnut and butternut are often called dru
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Keywords: ., bookauthoratk, bookcentury1900, bookdecade1900, booksubjectbotany
