Familiar lectures on botany, practical, elementary, and physiological : with an appendix containing descriptions of the plants of the United States and exotics, &c., for the use of seminaries and private students / by Almira H. Lincoln.
- Almira Hart Lincoln Phelps
- Date:
- 1836
Licence: Public Domain Mark
Credit: Familiar lectures on botany, practical, elementary, and physiological : with an appendix containing descriptions of the plants of the United States and exotics, &c., for the use of seminaries and private students / by Almira H. Lincoln. Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![open them at another ; almost every garden contains some plants in which this phenomenon may ho observed; it is particularly remanc- able in the sensitive plant, and the tamarind-tree. 1 his folding up of the leaves at particular periods, has been termed the sit ep ol plants; a celebrated botanist,* remarks, - this may be as useful to the vege- table constitution, as real s!e(p to the animal. Linnaeus was lea to observe the appearance of plants in the night, from a circumstance which occurred in raising the Lotus plan! ; he founa one morning some very thrifty flowers, but on looking for them at night, they were no longer visible. This excited his attention, and he began to watch then- unfolding. He was thus led to investigate the appear- ance of other plants at the same time, and to observe their different manner of sleeping. He found, as darkness approached, that some folded their leaves together, others threw them back, upon their pe- tioles, or closed their corollas, thus exhibiting a variety of interest- ing phenomena. This state of relaxation and repose seems to depend on the absence of light; with the first rays of the morning sun, the leaves recommence their chemical labours by drawing in oxygen, the fibres of the roots begin to imbibe sustenance from the earth, and the whole vegetable machinery is again set in motion. It is not so- lar light alone which seems capable of producing its effect on plants; this has been proved by the following experiment. A botanist placed the sensitive plant in a dark cave, and at midnight lighted it up with lamps; the leaves which were folded up, suddenly expanded ; and when, at midday, the lights were extinguished, they again as sud- denly closed. F'alllng of the Leaf. The period at which leaves fall is termed the Defoliation] of the plant. The fall of the leaf may be referred to two causes ; the death of the leaf, and the vital action of the farts to which it is at- tached. If a whole tree be killed by lightning, or any sudden cause, the leaves will adhere to the dead branches, because the latter have not the energy to cast them off. The development of buds, the hardening of the bark, and the formation of wood, accelerate the fall of the leaf. Heat, drought, frosts, wind, and storms, are all agents in their destruction. About the middle of autumn, the leaves of the Sumac and Grape- vine begin to look red, those of the Walnut, brown, those of the Honeysuckle, blue, and those of the Poplar, yellow; but all sooner or later take that uniform and sad hue, called the dead-leaf colour. The rich autumnal scenery of American forests is regarded by the European traveller with astonishment and delight, as far exceeding any thing of the kind which the old world presents. Painters, who have attempted to imitate the splendid hues of our forests, have, by foreigners, been accused of exaggeration ; but no gorgeous colour- ing of art can exceed the bright scarlet, the deep crimson, the rich yellow, and the dark brown, which these scenes present. After what you have now learned of the anatomy and physiology of leaves, you will probably be induced to pay attention to them in their different stages; from their situation in the bud, to their full growth and perfection ; you will feel a new interest in their change of colour, now that you understand something of the philosophy of this change;—even the dry skeletons of leaves, which the blasts of autumn strew around you, may not only afford a direct moral lesson * Sir J. E. Smith. t From de, signifying to deprive of, and folium, leaf. Sleep of plants—Cause of the sleep of plants—Defoliation—Fall o: the leaf!](https://iiif.wellcomecollection.org/image/b21147267_0062.jp2/full/800%2C/0/default.jpg)
