File:Text-book of botany, morphological and physiological (1875) (14774606551).jpg

Identifier: textbookofbotany00sach (find matches)
Title: Text-book of botany, morphological and physiological
Year: 1875 (1870s)
Authors: Sachs, Julius, 1832-1897 Bennett, Alfred W. (Alfred William), 1833-1902 Thiselton-Dyer, William T. (William Turner), 1843-1928
Subjects: Botany
Publisher: Oxford, Clarendon Press
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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l-wall filled either with air or with water. Older wood and corkwhen completely formed thus consist of a mere framework of cell-walls. But now arises an important difference between the behaviour of those cellswhich enclose a protoplasmic body, and of those from which it has already dis-appeared. The former only can grow, develop new chemical combinations, and,under certain conditions, form new cells. The latter are never capable of furtherdevelopment; if they are wood, they are of service to the plant only from their firm-ness, power of absorbing water, and from their peculiar form; if cork, they formprotecting envelopes which surround the living succulent cellular tissue. Since then no further process of development can take place in the cellswhich no longer contain protoplasm, it may be concluded that the latter is theproximate cause of growth. We shall see in a future paragraph that the de-velopment of each cell begins with the formation of a protoplasmic body, and that i.^—>
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FIG. 2.—Sexual reproduction of Fucks vesiculosus; A cellular filaments bearing antheridia ; B spermatozoids ; / Oogonium, Og withparaphyses /; //the exterior membranes of the oogonium is split, the inner 2 protrudes, containing the ova; ///an escaped ovum, withspermatozoids swarming round it ; Afirst division of the fertilised ovum ; IV 3. young Fucus resulting from the growth of the fertilisedovum (after Thuret, Ann. des Sci. Nat. 1854, vol. ii). (B X330; all the rest X160.) the cell-wall is also generated from it; but the relation of the protoplasm to cell-formation is still more strikingly conspicuous in those cases in which it continuesits life for some time as a naked sharply-defined solid body, and only at a laterperiod clothes itself again with a fresh cell-wall, and again takes up cell-sapwithin itself. We have an excellent example of this in the reproduction of theFucace^. On the fertile branches of these great marine Algae, of which we maytake Fiiciis vesiculosus as an exa

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