38 



MISC. PUBLICATION 110, U. S. DEPT. OF AGRICULTURE 



Figure 73. — Trun- 

 cate leaf, as in 

 yellow poplar, or 

 tuliptree (Lirio- 

 dendron tulipifera) 



to some external stimulus. For ex- 

 ample, geotropism (turning toward 

 the earth) is the tropism exhibited 

 by the root of a plant ; phototropism 

 (or heliotropism) is the turning or 

 response of the aerial portion of the 

 plant to the source of light. 



Truncate: Squared at the tip; termi- 

 nating abruptly as if cut off cross- 

 wise. (Fig. 73.) 



Tube: A tubelike 

 part, especially 

 the united, tu- 

 bular basal por- 

 tion of a gamo- 

 petalous corol- 

 la, as distinct 

 from the limb 

 or free portion. 



Tuber: A thick- 

 ened, usually 

 starchy (the 

 starch, how- 

 ever, replaced 

 in some tubers 

 by i n u 1 i n or 

 other carbohy- 

 drates) swelling of a subterranean 

 stem serving for food storage and 

 vegetative reproduction. Potato, 

 sweetpotato, dahlia, Jerusalem-arti- 

 choke, and yam furnish familiar ex- 

 amples of tubers. Tubers sprout 

 from buds known as eyes. 



Tuberculate: Beset with small, pimple- 

 like prominences (tubercles) as, for 

 example, the tuberculate nutlets of 

 certain species of the genus Oreo- 

 carya in the borage family. 



Tuberous : Of or pertaining to a tuber ; 

 resembling a tuber. 



Turbinate: Inversely conical; top 

 shaped. 



Turio (pi. -ones) : Same as turion. 



Turion (pi. -ns.) : A scaly shoot (often 

 thick and fleshy succulent) produced 

 from a bud on an underground root- 

 stock ; familiar examples are seen in 

 asparagus, cinnamon-vine, and vari- 

 ous mints. 



Type: The specimen or specimens on 

 which a species (or a subspecies or 

 variety) is based and from which 

 the author of that species (or sub- 

 species or variety) described it. For 

 example, the type of Pentstemon 

 mensarum Pennell is A. F. McDuf- 

 fie's plant specimen No. 151, United 

 States Forest Service range research 

 serial No. 7919, United States Na- 

 tional Herbarium (where deposited) 

 No. 1012411. 



Type locality: The place where a type, 

 or type specimen, was collected. 

 Thus, the type locality of Pentste- 

 mon mensarum Pennell, above men- 



tioned, is on the Grand Mesa (for- 

 merly Battlement) National Forest, 

 western Colorado. 



Typical: Having the characteristics of, 

 or well matching the type of a 

 species, variety, etc. 



Typonym: An absolute synonym in 

 nomenclature, being a name based 

 on the same type, specimen, or con- 

 cept as another and older name. See 

 synonym. 



U. S. N(at). H(erb).: The United 

 States National Herbarium. The 

 herbarium in the Smithsonian Insti- 

 tution, Washington, D. C, one of the 

 largest herbaria in the world, where- 

 in are deposited the plant types be- 

 longing to the Federal Government. 



Umbel: An indeterminate, convex or 

 flat-topped (umbrella-shaped) in- 

 florescence in which the rays or the 

 pedicels of the cluster arise from a 

 common point, the outer flowers 

 blooming earliest. (Fig. 74.) 



Figure 74. — Diagrammatic representa- 

 tion of a compound umbel (as in the 

 parsnip family) : a, Bractlets consti- 

 tuting involucels ; &, pedicel (individ- 

 ual flower stalk) ; c, ray ; d, bracts 

 constituting involucre ; e, peduncle : 

 f, flower. The flowers at the top 

 are arranged in umbellets (secondary 

 umbels) 



Umbellate : Borne in umbels ; umbel- 

 like. 



Umbellet: A small or secondary um- 

 bel ; the division of a compound um- 

 bel. ( Fig. 74, a. o, and f. ) In pars- 

 nip (Pastinaca), for example, each 

 main umbel is divided into about 7 

 . to 15 umbellets, each borne at the 

 apex of a ray. 



Umbellifer: A member of the umbelli- 

 fer, or parsnip, family (Umbelli- 

 ferae, Pastinaceae, or Apiacese). 

 Literally, umbel bearer. 



Uncinate : Hook shaped ; hooklike or 

 hooked. See barb. 



Undulate: With gently wavy margins. 

 Same as repand. (Fig. 60, B.) 



