. Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany. Botany. 434 THE VASCULAR PLANTS have germinated as internal parasites and thus the female gametophytes have been produced. One gametophyte matures in each megasporangium. It produces two or more eggs. (See Figure 226.) The sperms are in the pollen and the eggs are in the megasporangia. How are they to be brought together? C. The Pollen Tube. — You have learned of pollen tubes in your study of the flower. You know that they grow down through the styles, penetrate t
. Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany. Botany. 434 THE VASCULAR PLANTS have germinated as internal parasites and thus the female gametophytes have been produced. One gametophyte matures in each megasporangium. It produces two or more eggs. (See Figure 226.) The sperms are in the pollen and the eggs are in the megasporangia. How are they to be brought together? C. The Pollen Tube. — You have learned of pollen tubes in your study of the flower. You know that they grow down through the styles, penetrate the ovary, and that by means of them the sperms finally reach the eggs. Butg5Tnnosperms have neither ovaries nor styles. Their ovulfes are borne on the surface of the sporophylls and the pollen comes directly in contact with them. None the less, pollen tubes are needed and pollen tubes are produced. They are needed to penetrate that tissue of the ovule which separates the sperm from the Fig. 225.— A, seed-bearing pine cone {slro- bilus), cut so as to show the relation of the seeds to the scales {megasporophylls). B, a. young scale showing the position of the two ovules {^megasporangia). C, the two-winged seeds which develop from the ovules shown as they he upon the inner face of the scale. D. The Embryo. — After fertilization the pine cone en- larges until it reaches that full size with which you are most. 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 G. (John Gaylord), b. 1876. New York, American Book Co
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1913
