Sporangium.—The saclike case which contains the spores. See figs. [52] and [53], [p. 75].
Spore.—A single cell (generally protected by a cell wall) which has the power of germinating and reproducing the plant of which it is the reproductive body. See [p. 75].
Sporophyll.—A leaf or part of a leaf which bears spores or seeds, and which may be much or little modified.
Stele.—A strand of vascular tissue completely enclosed in an endodermis. See [p. 62].
Stigma.—A special protuberance of the carpel in flowering plants which catches the pollen grains.
Stomates.—Breathing pores in the epidermis, which form as a space between two curved liplike cells. See [fig. 23], [p. 54].
Tetrads.—Groups of four cells which develop by the division of a single cell called the “mother cell”. Spores and pollen grains are nearly always formed in this way. See [p. 75].
Tracheid.—A cell specially modified for conducting or storing of water, often much elongated. The long wood cells of Ferns and Gymnosperms are tracheids.
Underclay.—The fine clay found immediately below some coal seams. See [p. 24].
Vascular Tissue.—The elongated cells which are specialized for conduction of water and semifluid foodstuffs.