. The power of movement in plants . Plants; Botany. Chap. L aiLIUM. 59 by us of the part that first breaks through the ground not lieing arched. Fig Canna Warsceu-iczii: circumnutation of plumule with filament atTixed obliquely to outer sheath-like leaf, traced in darkness onhorizontal "Liss from Nov. 9th to 11th. Movement of bead mag- nified 6 times. Allium cepa (Liliaceae).—The narrow green leaf, which pro- trudes from the seed of the common onion as a cotyledon,* breaks thi-ough the ground in the forra of an arch, in the same manner as the hypocotyl or epicotyl
. The power of movement in plants . Plants; Botany. Chap. L aiLIUM. 59 by us of the part that first breaks through the ground not lieing arched. Fig Canna Warsceu-iczii: circumnutation of plumule with filament atTixed obliquely to outer sheath-like leaf, traced in darkness onhorizontal "Liss from Nov. 9th to 11th. Movement of bead mag- nified 6 times. Allium cepa (Liliaceae).—The narrow green leaf, which pro- trudes from the seed of the common onion as a cotyledon,* breaks thi-ough the ground in the forra of an arch, in the same manner as the hypocotyl or epicotyl of a dicotyledonous plant. Long after the arch has risen above the surface the apex remains within the seed-coats, evidently absorbing the still abundant contents. The summit or cruwn of the arch, when it first protrudes from the seed and is still buried beneath the ground, is simply rounded; but before it reaches the surface, it is developed into a conical protuberance of a white colour (owing to the absence of chlorophyll), whilst the adjoining parts are green), with the epidermis apparently rather thicker and tougher than elsewhere. We may therefore conclude that this conical protuberance is a special adaptation for breaking through the ground,! and answers the same end as the knife-like white crest on the summit of the straight cotyledon of the Graminese. * This is the expression used purpose wliich it suliserves. He by Siichs in his ' Text-book of states that good figures of the Botany.' cotyledon of the onion Ijave been t Habc-rlandt has briefly de- given by Tiltmann and by Saolis scribed (' Die Suhutzeinriohtun- iu his' Experimental Pbysiologie,' gen . .. Keimpflanze,' 1877, p. 77) p. this curious structure and the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882; Da
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Keywords: ., bookcentury1800, booksubjectbotany, booksubjectplants, bookyear18
