Sentence Examples


  • The spores, as in the heterosporous Pteridophyta, are of two kindsmicrospores (pollen grains) borne in microsporangia (pollen sacs) on special leaves (sporophylls) known as stamens, and macrospores (embryo-sac) borne in macrosporangia (ovules) on sporophylls known as carpels.
  • The male gametophyte is represented by one or few cells and, except in a few primitive forms where the male cell still retains the motile character as in the Pteridophyta, is carried passively to the macrospore in a development of the pollen grain, the pollen tube.
  • The ANGIOSFERMS, which are much the larger class, derive their name from the fact that the carpel or carpels form a closed chamber, the ovary, in which the ovules are developedassociated with this is the development of a receptive or stigmatic surface on which the pollen grain is deposited.
  • The sporophylls (stamens and carpels) are generally associated with other leaves, known as the perianth, to form a flower; these subsidiary leaves are protective and attractive in function and their development is correlated with the transport of pollen by insect agency (see ANGI0sPERM5; POLLINATION, and FLOWER).
  • The male gametophyte is sometimes represented by a transitory prothallial cell; ,the two male cells are carried passively down into the ovary and into the mouth of the ovule by means of the pollen-tube.

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