GLOSSARY OF BOTANICAL TERMS 



37 



typical panicle in that, while the 

 main axis is indeterminate, the 

 branches (secondary and ultimate 

 axes) are determinate and cymose. 

 Certain species of Oreocarya and 

 Pentstemon, as well as cultivated 

 lilac, horsechestnut and grapes, fur- 

 nish familiar illustrations of a thyr- 

 eoid inflorescence and fruit cluster. 

 The term is derived from the 

 thyrsus, or pinecone-tipped, Baccha- 

 nalian wand of antiquity. 



Tomentose: With a dense woollike 

 covering of closely entangled, matted 

 hairs (tomentum). 



Tomentulose: Sparingly or minutely 

 tomentose. 



Tomentum: Vegetable wool; densely 

 matted, woollike hairs. 



Tooth: A toothlike projection, as a 

 tooth on the margin of a leaf. 



Toothed: Provided with teeth, i. e., 

 toothlike projections, especially on 

 the margins ; dentate ; as a toothed 

 leaf or petal. 



Torose : Knobby ; knoblike ; provided 

 with bulging prominences, more or 

 less rounded but with alternate 

 swellings and contractions (Latin, 

 torosus, having bulging muscles). 

 As the torose pods of catclaw 

 (Acacia greggii). 



Torulose: Minutely torose; as in a 

 small pod constricted between the 

 seeds. 



Torus: A flower receptacle, or axis or 

 support of a flower head; a socket 

 or bed; a (usually round) swelling 

 or bulging; a knob or knot. 



Toxic: Poisonous; induced by poison- 

 ing. 



Toxicology: The science of poisons. 

 Plant or vegetable toxicology deals 

 with poisonous plants and their 

 toxic compounds (toxins). 



Toxin (e): A poisonous organic com- 

 pound, proteid in nature, occurrent in 

 or from certain secretions of plants 

 and animals. 



Tracheid: A more or less elongated, 

 often spindle-shaped woody (ligni- 

 fied) cell destitute of protoplasm, 

 the cells occurring end to end in 

 rows, the series of cells serving as a 

 sort of continuous, water-conducting 

 vessel. One of the two important 

 mechanical elements in the struc- 

 ture of wood, of which the other is 

 bast. Tracheids are especially char- 

 acteristic and constitute the bulk of 

 the wood of conifers, and their walls 

 are marked by bordered pits or other 

 markings due to unequal thicken- 

 ing in the wall structure. 



Transect: A cross seotion of vegeta- 

 tion, which may be a belt or merely 



a line, designed to show zonal dif- 

 ferences in the vegetation. In the 

 line transect the names of the in- 

 dividual plants are listed as they 

 are encountered along a measured 

 tape. In the belt transect, com- 

 monly delimited by two parallel 

 tapes at varying distances up to 

 a meter apart, the various species 

 encountered may be listed, tabu- 

 lated, or charted in their respective 

 places on the plotting paper. 



Transpiration: The giving off into the 

 atmosphere by the plant, mainly 

 through its stomata and from the 

 under surfaces of the leaves, of 

 water in the form of vapor. This 

 water represents a surplus from 

 that taken in from the roots and 

 which is not required for photo- 

 synthesis. Xerophytes, or desert 

 plants, exhibit many modifications 

 to reduce transpiration to a mini- 

 mum. 



Tree: An arborescent plant; a peren- 

 nial plant of considerable stature 

 with woody stems and a well-de- 

 fined, simple main stem (trunk or 

 bole). 



Tri-:A prefix (Latin) signifying three. 



Tribe: A group of related genera form- 

 ing a natural division of a family. 

 For example, the clover tribe (Tri- 

 foliese) of the bean family (Fab- 

 acese), which tribe embraces the 

 true clovers (Trifolium spp.), sweet- 

 clovers or melilots (Melilotus spp.), 

 alfalfas, bur clovers, medics, lu- 

 cernes, and snail clovers (Medicago 

 spp. ) , etc. Tribe is in practice often 

 loosely used as a synonym of sub- 

 family, but is actually a term of 

 lower rank and intermediate between 

 genus and subfamily. 



Trifoliolate: Having three leaflets; the 

 leaves 3-divided, as in clover and 

 alfalfa. (Fig. 72.) 



Figure 72. — Trifoliolate leaf, 

 as in clover 



Tropism: A turning or other reaction 

 of a plant or of its parts in response 



