. Text-book of botany, morphological and physiological. Botany. F1LICINEM. 445 arches convexly, and the prothallium is thus pushed further outwards. This is the present state of our knowledge with respect to the position of the prothallium in the macrospore. (Compare the explanations of the figures further on.) The prothallium of Salvinia natans attains a much more considerable size than that of the two other genera already mentioned; it contains abundance of chlo- rophyll, and forms a number (which may even be large) of archegonia in definite positions. After it has broken through the membran
. Text-book of botany, morphological and physiological. Botany. F1LICINEM. 445 arches convexly, and the prothallium is thus pushed further outwards. This is the present state of our knowledge with respect to the position of the prothallium in the macrospore. (Compare the explanations of the figures further on.) The prothallium of Salvinia natans attains a much more considerable size than that of the two other genera already mentioned; it contains abundance of chlo- rophyll, and forms a number (which may even be large) of archegonia in definite positions. After it has broken through the membrane of the papilla, it appears, seen from above, as three-sided between the three torn lobes of the epispore ; one of these sides is anterior; the two posterior sides meet behind at an acute angle; a line from this angle to the centre of the anterior side runs above the elevated saddle-shaped back of the prothallium, and forms its median line. The anterior side projects above the back, and, where it meets the two posterior. FIG. 312.—Development of the archegonia of Salvinia natans (after Pringsheim, x 150). FIG. 313.—Salvinia natans; median longitudinal section through the prothallium and young embryo ; A after the first three divisions of the oospore, / and // are separated by the basal wall; / the hypobasal segment divided by the wall y into the cells a and b; II the epibasal segment,divided by the wall 2 (transverse wall); cd axis of growth ; B embryo in a further stage of development, r rr first stage of the foot, s apical cell of the scutiform leaf, III—VI the succeeding segments, v apical cell of the stem ; m'vx A and B the closing cells of the archegonium (after Pringsheim).. 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 Sachs, Julius, 1832-1897; Vines, Sydney Howard, 1849-1934. ed. and tr. Oxf
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbotany, bookyear1882
