Lectures on the physiology of plants . As a rule the change consists in the leaves which are extended flat during the day,and which present their chlorophyll-surfaces perpendicularly to the incident light wherepossible, becoming folded together at night. With the commencing light of morningthe motile organs become curved, so that the laminae of the leaves situated on themagain assume the above-named extended diurnal position, while in the evening anopposite curvature of these organs produces the nocturnal position. This phe-nomenon has been termed the waking and sleeping of leaves ^ * The olde
Lectures on the physiology of plants . As a rule the change consists in the leaves which are extended flat during the day,and which present their chlorophyll-surfaces perpendicularly to the incident light wherepossible, becoming folded together at night. With the commencing light of morningthe motile organs become curved, so that the laminae of the leaves situated on themagain assume the above-named extended diurnal position, while in the evening anopposite curvature of these organs produces the nocturnal position. This phe-nomenon has been termed the waking and sleeping of leaves ^ * The older literature as to the periodic movements of leaves and flowers may be here passedover, inasmuch as it is treated in detail and criticised fully in Pfeffers works. I shall therefore 624 LECTURE XXXVI. But the foliage-leaves of very many other plants also, in which no specialmotile organs are observable, make daily movements resulting in the production ofdiurnal and nocturnal positions: the growing petioles undergo curvatures by which. FIG, :ß^.—Des»wdi ryrans. A slioot during the day ; B shootFrom reduced photographs (Darwin). the laminae situated on them are presented to the light during the day, and at nightare directed upwards or downwards. mention only a few more recent works which will at once place the beginner on the right path inthis province. Sachs, Über das Bczuegitngsorgan und die periodische Bewegungen der Blätter von Phaseolusund Oxalis, Bot. Zeit. 1857 (p. 793). Sachs, Die vorübergehenden Starrezustände periodisch beweglicher jind reizbarer Pßanzen-organe, Flora, 1863 (Nos. 29, &c.). Paul Bert, Memoir, d. l. soc, d. et naturell, d. Bordeaux (1866). Millardet, Nouv. recherches sur la pcriodicitc d. l. tension^ 1869 (Mem. de la soc. natur. deStrasbourg). Batalin, Über die Ursachen der periodischen Bezuegungen der Blumen und Laubblätter^ Flora, 1873 (P- 433)- Pfeffer, Physiologische Untersuchungen Leipzig (1873 and 1875). Sachs, Lehrbuch der B
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectplantph, bookyear1887
