Text-book of botany : morphological and physiological / by Julius Sachs ; translated and annotated by Alfred W. Bennett ; assisted by W.T. Thiselton Dyer.

Date:
1875
Catalogue details

Licence: Public Domain Mark

Credit: Text-book of botany : morphological and physiological / by Julius Sachs ; translated and annotated by Alfred W. Bennett ; assisted by W.T. Thiselton Dyer. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    and some climbing Palms like Calamus, &c., whose long shoots spread over neighbouring plants and are supported by 4hem, their hooked prickles and other similar contrivances assisting in this. It is of service to many plants in the struggle for existence that they should keep firm possession of the piece of ground they have once occupied, without forming for this purpose large woody masses, like trees and shrubs. The under- ground parts of such plants are perennial, and they send up separate shoots in each vegetative period to be exposed to the light and air where they will be able to assimilate, to produce flowers, and to scatter their seeds. This persistence of the underground parts has the advantage that the plant, although it assimilates and grows only at particular times of the year, is not compelled to seek each year, like annual plants, a new locality in which its seeds may germinate. The collection of reserve food-materials underground gives strength to the plant; it developes its buds beneath the soil to such an extent that at the right time they can grow up quickly at the expense of the rich supply of food. Every year very strong shoots are put forth, while in annual plants a number of feeble seedlings perish annually before some of them attain sufficient strength to protect themselves from the shade and humidity to which their neighbours subject them. Plants whose underground parts are perennial have in particular the power of resisting long and severe frost and the greatest variations of temperature, because these only penetrate slowly beneath the soil. It is for this reason that so large a number of Alpine and Arctic plants belong to this class. They are also able to grow in localities which are much too dry for the germination of the seeds of annual plants, because moisture is retained at a great depth for a longer period than near the surface. Numerous other advan- tages might also be mentioned which are of course secured to annual plants by other adaptations This permanence of the underground parts is attained in the greatest variety of ways. Sometimes the plant possesses slender creeping underground shoots in which the reserve food-materials are collected and which themselves rise above the surface at a particular time, as in many Grasses; or sometimes the leafy stems are developed from lateral buds, as in Equisetum; or there are thick stout stems from which shoots appear each year at the same place. In some cases the whole plant is annually renewed; all the parts which existed the previous year die off, and a complete rejuvenescence of the individual is accomplished underground. In the potato and artichoke only the apical parts of the underground lateral shoots swollen into tubers remain over till the next year, the whole of the rest of the plant having perished. In many of our native Orchids the rejuvenescence takes place in a similar way (see p. x 99 and fig. 150); and one of the most interesting cases of annual rejuvenes- cence occurs in Colchicum autumnale (see fig. 391, p. 545). In these cases, with the exception of the Orchids, the reserve food materials accumulate in underground parts of the axis; in other cases this takes place in the swollen roots, which remain in connection with the underground part of the stem that bears the new buds, as 1 [This subject—and especially the relation of peculiar habits of life to the power of resisting great cold—is very fully discussed in Kerner’s treatise Die Abhangigkeit der Pflanzengestalt von Klima und Boden, Innsbruck, 1869.—Ed.]