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       In the following names, the stressed vowel is the one preceding the stress mark. It is not always easy to ascertain where such stress should be placed, especially in the case of epithets derived from personal names. I have tried to follow the principle of maintaining the stress of the original name as outlined in the Jepson Manual, and have abandoned it only when it was just too awkward. In the case of some names, I have listed them twice, reflecting either some disagreement or conflict in the rules of pronunciation, some uncertainty on my part as to the correct pronunciation, or that simply sometimes there is no single correct pronunciation. In other instances, the way I record it is just that which sounds right to my ear.

• uh'dei: after Carl Adolph Uhde (1795-1856) who travelled through Texas and northern Mexico 1849-1855 and wrote about natural features, Mexican political affairs and the history of Europeans in that area (ref. Fraxinus uhdei)
• -ulentum/ulentus: a Latin adjectival suffix used to indicate an abundance of or a full or marked development of (e.g. succulentus, "full of juice" from succus, "juice")
• Ul'ex: the ancient name of this or some similar plant (ref. genus Ulex)
• uligino'sum/uligino'sus: of swamps and wet places (ref. Delphinium uliginosum, Vaccinum uliginosum, Lotus uliginosus)
• ulmifo'lius: with leaves like genus Ulmus (ref. Rubus ulmifolius)
• Ul'mus: the classical Latin name for the elm (ref. genus Ulmus)
• -ulosa: this is a suffix which on some names does not seem to covey much difference from the same names with the -osa suffix, e.g. ramosa and ramulosa, "with many branches." More often though there does seem to be a slight difference as with strigosa, "bearing straight, stiff, appressed hairs" and strigulosa, "minutely strigose;" fruticosa, "shrubby," and fruticulosa, "somewhat shrubby and small;" lanosa, "woolly," and lanulosa, "minutely woolly;" spinosa, "spiny," and spinulosa, "minutely spiny;" and tomentosa, "covered with matted, woolly hair," and tomentulosa, "slightly tomentose." So perhaps the sense of this suffix is usually that of "slightly" or "minutely" or "somewhat." Most commonly there are names for which there appear to be only a single form of the name, like glandulosa, maculosa, villosa, tubulosa, dumosa, tuberosa, corymbosa, racemosa, tumulosa and many other examples.
• ultraal'sa: from the Latin alsus, "cold, chilly," and ultra, "beyond, in excess." Michael Windham in Harvard Papers in Botany Vol. 11 Issue 1 (July 2006) says: "It is a strikingly distinct species that, when first encountered, elicited a response ("beyond cool") that we Latinized to form the specific epithet. Alternatively the name also reflects the geography on the 'SW side (beyond) of Snow Mt. (a cool place)'." (ref. Boechera ultraalsa)
• ultrama'fica: the word 'mafic' means 'of or pertaining to rocks rich in dark, ferromagnesian minerals,' so this name may imply that the species which bears it inhabits soils that derive from these kinds of rocks or are rich in these kinds of minerals (ref. Frangula purshiana ssp. ultra-
  mafica)
• ultramonta'na: possibly for high mountains
• -ulum/-ulus: either (1) a Latin adjectival suffix used as a diminutive (e.g. patulum, "somewhat spreading," hispidulus, "minutely or somewhat hispid"; dracunculus, "a small dragon," from draco, "dragon"; cardunculus, "a small thistle," from carduus, "thistle"), or (2) a suffix which indicates a tendency or action (e.g. pendulus, "hanging down," from pendere, "to hang"; convolvulus, "twining around," from convolvere, "to roll up, coil up, intertwine")
• umbella'ta/umbella'tum: refers to the arrangement of the flowers which arise in a head from a central point, i.e. bearing an umbel (ref. Abronia umbellata, Chimaphila umbellata, Comandra umbellulata, Hydrocotyle umbellata, Calyptridium umbellatum, Eriogonum umbellatum var. subaridum, Eriogonum umbellatum var. minus, Eriogonum umbellatum var. munzii, Eriogonum umbellatum var. nevadense)
• umbellif'erum: bearing an umbel (ref. Solanum umbelliferum)
• Umbellular'ia: pertaining to umbels (ref. genus Umbellularia)
• umbraculor'um: from the Latin umbraculum, "a shady place, bower, arbor," thus meaning "of shady places, bowers, arbors" (ref. Delphinium umbraculorum)
• umbrat'icus: from the Latin umbratus, "shading, spreading over" from umbro, "to shade," and the suffix -icus, a Greek adjectival suffix indicating a state of belonging to, thus according to Jaeger's Source-Book of Botanical Names and Terms meaning "belonging to shade, belonging to seclusion" (ref. Astragalus umbraticus)
• umbrinel'la: from the Latin umbrinus, "darkened, shady," and the adjectival suffix -ella, which is a diminutive, thus meaning "slightly darkened"
• umbro'sa: shade-loving (ref. Phacelia umbrosa)
• unalascen'sis: refers to Aleutian Islands (Unalaska) where species was first found (ref. Piperia [formerly Habenaria] unalascensis)
• uncia'lis: one-twelfth, an inch, from Latin uncia, a twelfth, of unknown application (ref. Erigeron uncialis, Juncus uncialis)
• uncina'tum/uncina'tus: hooked at the end (ref. Chamelaucium uncinatum, Plagiobothrys uncinatus, Ranunculus uncinatus)
• unda'tus: waved, wavy
• undo'sus: same as previous entry, referring to the lower stem leaves which are said to be wavy on the margins (ref. Penstemon eatonii var. undosus)
• undula'ta/undula'tum/undula'tus: wavy-margined (ref. Hesperocallis undulata, Cirsium undulatum, Pittosporum undulatum, Plagiobothrys undulatus)
• unguicula'ta: Latin for "little red nail or claw" referring to the unusual claw at the base of the petals (ref. Clarkia unguiculata)
• uniarista'ta: from the roots uni, "one, single," and aristata, "bearded or furnished with an awn" (ref. Chorizanthe uniaristata)
• uniflor'a/uniflor'um: single-flowered (ref. Orobanche uniflora, Pyrrocoma [formerly Haplopappus] uniflora var. gossypina, Ipheion uniflorum)
• unifo'lium: single-leaved (ref. Allium unifolium)
• unilatera'lis: one-sided (ref. Carex unilateralis, Heterodraba unilateralis, Poa unilateralis)
• uniner'via: with a single nerve (ref. Leptochloa uninervia)
• unispica'ta: with a single spike (ref. Danthonia unispicata)
• urceola'ta: urn-shaped
• ur'ens: stinging, burning (ref. Eucnide urens, Urtica urens)
• Urochlo'a: from the Greek oura, "a tail," and chloe or chloa, "grass," in reference to the awns (ref. genus Urochloa)
• Uropap'pus: with the pappus having a long tail-like dip (ref. genus Uropappus)
• Urosper'mum: from the Greek oura, "a tail," and sperma, "a seed," alluding to the tail-like beak of the seeds (ref. genus Urospermum)
• ursin'a/ursin'um/ursin'us: from the Latin ursus, "a bear," referring to one of a bear's favorite foods, or possibly a reference to being northern, i.e. under the northern constellation called the Great Bear (ref. Arenaria ursina, Rubus ursinus)
• Ur'tica: from uro, "I burn," alluding to the nettle's sting (ref. genus Urtica)
• urticifo'lia: having nettle-like leaves (ref. Agastache urticifolia)
• uruguayen'sis: of or from Uruguay (ref. Ludwigia uruguayensis)
• urvillea'num: after French navigator Jules Sébastien César Dumont D'Urville (1790-1842). The Columbia Encyclopedia entry on D'Urville reads as follows: "While on duty (1819-20) in the E. Mediterranean, he saw and recognized the importance of the newly discovered Venus of Milo and was influential in having the Louvre secure it. In 1822-1825, while serving on the Coquille, he surveyed the Falklands, Tahiti and other Pacific islands, and New Holland (W. Australia). In 1826-1829 he commanded the Astrolabe in a voyage around the world; searching for the ill-fated La Pérouse expedition, he explored Fiji and many other islands of Oceania, the New Zealand coast, and the Moluccas. With the Astrolabe and the Zelée he made a second circumnavigation in 1837-1840, and in 1840 he penetrated the ice pack south of New Zealand and discovered the Adélie Coast region in Antarctica." He brought back to France a very fine collection of animals and plants from one of his round the world voyages. He was eventually promoted to the rank of rear admiral and the Geographical Society awarded him their highest honor, the Gold Medallion. He was killed along with his wife and son in a train accident in 1842 near Versailles. (ref. Panicum urvilleanum)
• urvil'lei: see previous entry (ref. Paspalum urvillei)
• usitatis'simum: from the Latin usitatus, "customary, common, familiar," from usitor, "to use often, to be in the habit of using," and the -issimum suffix which conveys the sense of "most or very," thus this would be "most or very customary, common or familiar." Stearn's Dictionary of Plant Names gives "most useful" as the meaning, but "most used" and "most useful" don't exactly have the same sense so I'm not sure about this (ref. Linum usitatissimum)
• usita'tus: see previous entry (ref. Juncus usitatus)
• ustula'ta: burned, scorched, sere (ref. Gamochaeta ustulata)
• utahen'se/utahen'sis: of or from Utah (ref. Cynanchum utahense, Agave utahensis, Amelanchier utahensis, Buddleja utahensis, Claytonia parviflora ssp. utahensis, Cryptantha utahensis, Erigeron utahensis, Fendlerella utahensis, Mortonia utahensis, Penstemon utahensis, Salicornia utahensis)
• uti'lis: useful (ref. Muhlenbergia utilis)
• Utricular'ia: from the Latin utriculus, "a small bag or bladder," the common name of which is bladderwort (ref. genus Utricularia)
• utricula'ta/utricula'tum: with a small bladdery one-seeded fruit, bladder-like (ref. Carex utriculata, Lomatium utriculatum)
• -utum/-utus: a Latin adjectival suffix used to indicate possession (e.g. argutum, "sharply-toothed, possessed of teeth or notches"; cornutus, "horned, possessed of horns," from cornu, "horn"; acutus, "possessed of a sharp point")
• uv'a-ur'si: literally means "bear's grape" referring to the fruit (ref. Arctostaphylos uva-ursi)
• uvar'ia: from the Latin uva for a bunch of grapes (ref. Kniphofia uvaria)