356 INTRODUCTION TO BOTANY 
Stamen. The microsporophyll in spermatophytes. 
Stigma. That portion of the surface of a pistil (without epidermis) 
which receives the pollen. 
Stigmatic. Relating to the stigma, or stigma-like. 
Stoma (a mouth); pl. stomata. Epidermal structures which serve for 
facilitating gaseous interchanges with the external air, and for transpi- 
ration of moisture. They are often incorrectly called “ breathing pores.” 
Strobilus. A cone-like cluster of sporophylls. 
Style. The usually attenuated portion of the pistil which bears the 
stigma. 
Succulent. Thick and fleshy. 
Suspensor. A chain of cells which develops early from the odspore, 
and serves to push the embryo cell deep within the embryo sac. 
Symbiont. One of the organisms that has entered into a symbiotic 
relationship. 
Symbiosis (living together). Applied to a condition in which two or 
more organisms are living in an intimate relationship. 
Sympetalous. Having the petals apparently all united, as if grown 
together by their edges. 
Syncarpous (carpels united). Applied to those conditions in which 
the carpels have united into a compound pistil. 
Synergids (helpers). The two nucleated bodies which accompany the 
oésphere in the embryo sac, and together with it form the egg apparatus. 
Testa (a shell). The outer seed coat. 
Tetracyclic (four cycles). Applied to those flowers in which there are 
four cycles of floral organs. 
Tetradynamous (four strong). Said of a stamen cluster in which there 
are four long and two shorter stamens. 
Thalloid. Thallus-like. 
Thallus (a young shoot). The body of lower plants, which exhibits 
no differentiation of stem, leaf, and root. 
Tissue. A texture built up of mutually dependent cells of similar 
origin and character, as the cambium layer. 
Tracheid. A long, slender cell, with closed ends and its walls thick- 
ened after the cell has attained its full size, as in the pitted cells of 
coniferous wood. 
Transpiration. The loss of water derived from the interior of the 
plant body in the form of vapor. The term is not generally used with 
reference to plants of low organization. 
Trichome (a hair). A general name for a slender outgrowth from the 
epidermis, usually arising from a single cell. 
Turgidity. The normal swollen condition of active cells which results 
from the distension brought about by absorption of water. 
