. Botany for agricultural students . Botany. 454 SPERMATOPHYTES (SEED PLANTS) gether, but they do not form close clusters as the staminate cones do. The scales of the ovulate cones are considered too complex to be called sporophylls, for each scale consists of an ovuUferous scale (ovule-bearing scale) and a bract, the two being partly united. Some morphologists think that the ovuliferous scale itself repre- sents two sporophylls fused together. The megasporangia or. Fig. 403. — The ovulate structures of the Pine. A, branch bearing four ovulate strobili, B, ovulate strobilus, showing the arrang
. Botany for agricultural students . Botany. 454 SPERMATOPHYTES (SEED PLANTS) gether, but they do not form close clusters as the staminate cones do. The scales of the ovulate cones are considered too complex to be called sporophylls, for each scale consists of an ovuUferous scale (ovule-bearing scale) and a bract, the two being partly united. Some morphologists think that the ovuliferous scale itself repre- sents two sporophylls fused together. The megasporangia or. Fig. 403. — The ovulate structures of the Pine. A, branch bearing four ovulate strobili, B, ovulate strobilus, showing the arrangement of scales (X about 2); C, a view of the inner or upper side of a scale, showing the two sporangia (s). ovules, two in number, are borne on the upper side and at the base of the ovuliferous scale {Fig. 403). The scales are spirally arranged and closely crowded, but during pollination they spread apart, and the pollen can slide in between them and reach the ovules. After pollination the scales close together again, and the cone is made water-tight by a secretion of resin. After pollina- tion the cone also changes from the vertical to the nodding position. The ovules consist of an integument and a nucellus, and deeply buried within the nucellus the four megaspores occur. The ovules are arranged one on each side of the median line of the scale, with the micropyles pointing downward. The integument. 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 Martin, John N. (John Nathan), b. 1875. New York : John Wiley & Sons, Inc.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
