GLOSSARY 191 



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 endo- 

 dermis. 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. 



