. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. THALLUS OF GREEN ALG^ 197 are found in young stages of most filamentous Algae (Figs. 115, a ; 117, g), but in forms like Spirogyra, (Edogonitim, and Ulothrix, the filaments usually break off and become free-floating as they grow older, except in the case of species inhabiting flowing water. The lobes of the attaching cells grow into all the irregularities of the substratum (Fig. 104, B), to which they cling after the manner of a sucker, adhesion being often increased by the secre- tion of a cementing substanc
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. THALLUS OF GREEN ALG^ 197 are found in young stages of most filamentous Algae (Figs. 115, a ; 117, g), but in forms like Spirogyra, (Edogonitim, and Ulothrix, the filaments usually break off and become free-floating as they grow older, except in the case of species inhabiting flowing water. The lobes of the attaching cells grow into all the irregularities of the substratum (Fig. 104, B), to which they cling after the manner of a sucker, adhesion being often increased by the secre- tion of a cementing substance. The great efficiency of the at- taching cells is very evident in those species of Cladophora which grow on wave- beaten rocks or in rapidly flowing streams. The restriction of the power of division to the terminal cells of Cladophora marks a considerable step in the direction of divi- sion of labour as com- pared with Ulothrix, and this is also seen in the formation of reproductive units, which is almost con- fined to the cells of the lateral branches (cf. p. 215). A more extreme condition is seen in Draparnaldia (Fig. 105), which is not uncommon in slowly flowing water. Here the main axes, which serve almost solely for support, consist of large cells with smaU chloroplasts, whUst assimilation and reproduction are relegated to the densely branched Fig. 105.—Photograph of part of a plant o the Green Alga Draparnaldia, seen under the low power of the microscope. [Photo : E. J. S.]. 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 Fritsch, Felix Eugene, 1879-; Salisbury, E. J. (Edward James), Sir, b. 1886. London, G. Bell and sons ltd.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpl, booksubjectplants
