1175 



Oje Etmsuri) of iootanij. 



[trit 



base ; glumes two, lance-shaped three- 

 nerved, channeled and herbaceous, the 

 npper slightly the longest; pales two, her- 

 baceous "and pointed. Steudel describes 

 seven species, which are natives of South 

 America and South Africa. [D. MJ 



TRISTAN I A. A genus of Australian 

 shrubs, of the myrtle family. They have 

 linear leaves, and yellow flowersin corymbs; 

 calyx five-cleft; petals Ave; stamens ar- 

 ranged in live parcels, opposite the petals; 

 fruit capsular, many-seeded ; seeds without 

 wings. Some of the species are grown as 

 pretty greenhouse plants. [M. T. M.] 



TRISTEMMA. This genus of Melasto- 

 macece consists of certain tropical African 

 shrubs with four-sided stems, and flowers 

 in heads surrounded by involucres. The 

 calyx is provided with a projecting rim or 

 rims near to its four or five-lobed limb ; 

 the petals are stalked ; the stamens eight 

 to ten, equal, their anthers opening by 

 one pore , the ovary is confluent with the 1 

 tube of the calyx, and contains four or 

 five compartments, which open at the hairy 

 apex when ripe. [M. T. M.] 



TRTSTICHA. A genus of Podostemacece, 

 comprising species which grow in wet 

 places in Brazil, Southern Africa, and Mada- 

 gascar. Theyarelittlemoss-likeplants,with 

 much-branched slender annual stems. The 

 perianth is membranous and three-parted, 

 concealing a single stamen, and a stalked 

 three-ceiled ovarysurmounted by three stig- 

 mas. Thefruitis three-celled, three- valved, 

 and marked by nine ribs. [M. T. MJ 



TRISTICHOUS. In three rows. 



TRISTIS. Dull-coloured. 



TRITBLBIA. A small genus of LUiacece, 

 from Western North America and Buenos 

 Ayres. It has a salver-shaped perianth, 

 with a six-parted limb, six stamens in two 

 I rows, a trilobed stigma, and a many- 

 | seeded ovary. The leaves are linear, and 

 the scapes bear involucrate umbels of 

 white or bluefl >wers, or in some of the spe- 

 cies simple peduncles bear solitary flowers. 

 T. laxa, a native of California, has glau- 

 cous leaves, and a many-flowered umbel of 

 deep-blue flowers. T. unifiora is a very 

 handsome white-flowered species. [J. T. S.] 



TRITERNATE. "When a common petiole 

 divides into three secondary petioles, which 

 are each subdivided into three tertiary 

 petioles, each bearing three leaflets. 



TRITHRINAX. A genus of Palmacece, 



of which three species are described :—T. 



I brasiliensis, that upon which the genus 



; was founded, a native of Rio Grande, the 



most southern province of Brazil ; T. acii- 



leata, a native of Western Mexico ; and T. 



i mauriticeformis, of New Granada. They 



j are all low growing palms, with the lower 



' part of their trunks marked by close cir- 



| cular scars, and the upper clad with the 



persistent bases of old leafstalks. They 



! have deeply-cut fan-shaped prickly-stalked 



I leaves, with threads hanging from between 



| the segments ; and much-branched spikes 



of greenish-yellow flowers, which are either 

 perfect or (by abortion) of one sex only 

 The perfect ones contain six free or slight- 

 ly connected stamens, rising from the bot- 

 tom of the corolla, and three distinct 

 ovaries with narrow tapering styles and 

 simple stigmas. Only one of the ovaries 

 conies to maturity, forming a one-seeded 

 fruit, the seed having the embryo placed 

 at the back near the top. [A. S.J 



TRITICUM. A genus of grasses of the 

 tribe H ordece, which includes, among other 

 species— T. vulgare, or Common Wheat; T. 

 repens, the Creeping Couch or Cooch ; and 

 T. caninum. T. vulgare is an annual cereal 

 or corn-grass, which under the name of 

 Wheat is well-known to every one. Its 

 varieties, though endless, may perhaps be 

 all comprehended under the following 

 heads, of each of which we may have va- 

 rieties, with more or less hairiness on the 

 chaff -scales, &c. :— T. vulgare muticum \T. 

 hybernum. Linn.), the awn less or Beardless 

 "Wheat; T. vulgare barb atum (T astivum, 

 Linn.); and T. Spelta, the grains in which 

 are more or less adherent to the chaff- 

 scales. 



The native country and origin of Wheat 

 has ever been a curious subject of specula- 

 tion. We think, however, that M. Fabre's 

 experiments, detailed in the Journal of 

 the Royal Agricultural Society, afford very 

 strong presumptive evidence that this ce- 

 real isderived from a wild grass of Southern 

 Europe and Western Asia, known to the | 

 botanist as ^Egilops : which see. It is true I 

 that a specimen of this genus would at first 

 sight appear to be very different from j 

 wheat, but it is really not so on a minute 

 examination of its parts, and under cultiva- j 

 tion it soon affords a very respectable grain ; I 

 its green herbage, too, emits the peculiar | 

 smell on being bruised which belongs to | 

 wheat, and, as we know from experiment, j 

 it is subject to the same epiphytes or at- I 

 tacks of ' blight 'as wheat. Thata plant very i 

 dissimilar from wheat, in fact a wild use- j 

 less grass, should yet in cultivation become 

 so changed as to afford a useful grain, is 

 so far fortunate in that we might expect, 

 from this amount of adaptability to cir- 

 cumstances, that it would be capable of 

 easily affording a large variety of sorts, i 

 Such we know to be the case, and hence no | 

 plant is so easily adapted to variations of 

 climate, soil, and management as wheat. 



Our wild species of the genus are peren- 

 nial grasses. T. repens, the Couch, is by 

 far too well and unfavourably known to 

 merit our dwelling upon it at great length. 

 This has been split up into several species 

 by some botanists, which has arisen from 

 its capabilities of changing from circum- 

 stances; for, like its cultivated ally, it is 

 bearded or beardless, and can adapt itself 

 to all positions. T. camnum differs from 

 it mainly in the absence of the running 

 underground stems (rhizomes). It has, 

 however, the same pungent flavour which 

 belongs to all the Tritici, due probably to 

 the presence of some kind of essential oil, 

 in virtue of which it would appear to he 



