442 PLANT MORPHOLOGY 



Suspensor. In many pteri(lo})hytes and spermatophytes, an appendage to the 

 embryo, both derived from the zygote. 



Symbiosis. The living together, in intimate association, of two dissimihir organisms 

 to their nnitiial advantage. 



Sympetalous. Having petals more or less united. 



Sympodium. An apparent main axis composed of successive secondary axes, each rep- 

 resenting one fork of a dichotomy, the other being weaker or entirely suppressed. 



Synangium. A group of sporangia developed as a single structure, as in some ferns. 



Syncarpous. With united carpels. 



Synergid. In angiosperms, one of a pair of cells accompanying the egg and with it 

 forming the egg apparatus. 



Tapetum. In pteridophytes and spermatophytes, one or several layers of nutritive 

 cells investing the sporogenous tissue in a young sporangium. 



Teliospore. In the rust fungi, a thick-walled spore, commonly bilocular and stalked, 

 that produces a basidium when it germinates, generally after a period of dor- 

 mancy. 



Telium. A group of teliospores. 



Tetracyclic. Having four cycles or whorls of floral parts. 



Tetrad. A group of four cells formed by two successive divisions of a spore mother 

 cell. 



Tetramerous. Having the floral parts in sets of four or multiples of four. 



Tetraspore. In certain red algae, one of the nonmotile spores produced in a group of 

 four in a sporangium. 



Thallus. A vegetative body without differentiation into true roots, stems, and leaves. 



Trabecula. A plate of cells bridging an intercellular space or extending partially or 

 completely across the cavity of a sporangium. 



Tracheid. A slender, elongated, nonliving, water-conducting cell with tapered, closed 

 ends and thickened, lignified walls. 



Trichogyne. In the red algae, a thread-like extension of the carpogonium; in the 

 ascomycetes, a tubular outgrowth of the ascogonium. 



Trilocular. Having three locules or cavities. 



Trimerous. Having the floral parts in sets of three or multiples of three. 



Triploid. Having three times the basic or haploid chromosome ninnber. 



Tunica. The outer growth zone in a stem tip, consisting of one or several superficial 

 layers of embryonic cells. 



Undulate. Having a wavy surface or margin. 

 Unicellular. One-celled. 

 Uniciliate. Having a single cilium. 

 Unilocular. Having a single locule or cavity. 

 Uredinium. A group of uredospores. 



Uredospore. In the rust fungi, a unicellular spore, commonly borne singly on a stalk, 

 and generally capable of producing a mycelium at once. 



Vacuole. A cavity or vesicle in the protoplasm of a cell, containing a watery fluid, the 



cell sap. 

 Vallecular canal. In the Equisetinae, one of the canals in the cortex of the stem and 



lying beneath a groove on the surface. 

 Vascular bundle. A strand composed primarily of vascular tissue traversing some 



part of the plant. 



