. A text-book of botany for secondary schools. Botany. LIVERWORTS 167 The plant body is flat and compact, lying prostrate upon its substratum, and is often a thallus; that is, it shows no distinction of stem and leaves, the whole body appearing leaf-like (Fig. 160). The upper surface of the body is freely exposed to the light, but the lower surface is against the substratum and puts out hair-like processes (rhizoids) for anchorage. If the body is thin, all the cells contain chloroplasts; but if the body is so thick that the light cannot penetrate it, the under layers of cells are not green. 92
. A text-book of botany for secondary schools. Botany. LIVERWORTS 167 The plant body is flat and compact, lying prostrate upon its substratum, and is often a thallus; that is, it shows no distinction of stem and leaves, the whole body appearing leaf-like (Fig. 160). The upper surface of the body is freely exposed to the light, but the lower surface is against the substratum and puts out hair-like processes (rhizoids) for anchorage. If the body is thin, all the cells contain chloroplasts; but if the body is so thick that the light cannot penetrate it, the under layers of cells are not green. 92. Marchantia.—Marchantia is one of the most com- mon and conspicuous liverworts. The body is a thick. Fia. 161.—Marchantia, cross-section of thallus: showing lower epidermis (from which, in other parts of the thallus, rhizoids are developed), two layers of colorless cells (p), and one large air-chamber (a, s, the bounding walls) contain- ing cells with chloroplasts (cAZ) and pierced by a chimney-like air-pore {sp).— After GoEBEL. thallus that forks repeatedly, giving the appearance of notches of greater or less depth (general habit as in Fig. 160). The central axis of the thallus, or of a branch, ends in the terminal notch, in the bottom of which, therefore, is the growing tip. The upper surface of the Marchantia body is blocked off into small rhombic areas, in the center of each one of which is a minute opening (Fig. 162). A section through this body shows its general structure (Fig. 161). Beginning with the lower side, there is seen first the layer of cells forming the epidermis, from which the rhizoids and certain other appendages arise; above this 12. 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 Coulter, John Merle, 1851-1928. New York, D. Appleton
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1906
