GEISSOMERIA GEOLOGY. 



621 



of brown, divided from each other by deep red. It 

 is found in several of the West India islands, as are 

 also some other species or varieties about the same 

 size, but differently coloured. 



There are several other saurian reptiles which 

 agree with the geckos in most of their characters, but 

 differ from them in not having the toes enlarged, in 

 having claws upon all the toes, and those claws not 

 retractile. Of these we may just mention 



Stcnodactyli, which have the tail round, the toes 

 striated below, and toothed on the sides. The prin- 

 cipal species having these characters is found in 

 Egypt. Its covering is smooth, of a grey colour, 

 spotted with white. 



Gymnodactyli, as the name imports, have the toes 

 naked and slender, but the name is usually restricted 

 to such as have the tail round, which are American 

 species. The others, which have so peculiar a cha- 

 racter of the tail, that they ought, strictly speaking, 

 perhaps to form a separate genus, are 



Phyllurus, leaf-tail. These are inhabitants of New 

 South Wales. Their toes are not enlarged like those 

 of the geckos, but the tail is flattened in the form of 

 a leaf. This organ is so exceedingly brittle, that it 

 is rare to find a specimen having it entire. One 

 species (P. Cuvierii), which is found in marshy places 

 in the neighbourhood of Port Jackson, and lives 

 there upon aquatic insects and larva;, is covered over 

 with pointed tubercles. Its head is elongated, its 

 jaws pointed, its colour on the upper part marbled 

 with brown, and its tail in the form of a fibrous and 

 partially twisted leaf. Another species (P. J\filii'), is 

 smaller than the former, but longer in the legs, blunt 

 in the head, and of a brick-dust colour on the upper 

 part, so that it is not easily distinguished from the 

 ground which it inhabits. The enlarged portion of 

 the tail is near the extremity, and it has a very 

 strange appearance, as if it were an appendage not 

 natural, or apparently of any use to the animal, but 

 added to render its appearance more singular. 



GEISSOMERIA(R. Brown). An elegant flower- 

 ing shrub, introduced from Brazil, belonging to Di- 

 dynamia angiospermia, and to the natural order Acan- 

 thacecE. Generic character : calyx bracteate in five 

 unequal parts, the back segment largest ; corolla 

 funnel-shaped, limb of two lips, the upper one tvvo- 

 lobed, the lower three-lobed ; anthers linear and two- 

 celled ; stigma thickish ; seed vessel two-celled and 

 four-sided. These plants require a rather rich soil, 

 in which they produce the scarlet flowers in abund- 

 ance in the stove. They are propagated by cut- 

 tings. 



GENIPA (Tournefort). A genus of South Ame- 

 rican fruit trees, belonging to the fifth class and first 

 order of the Linmean system, and to the natural order 

 Rubiacece. Generic character : calyx truncate entire ; 

 corolla salver-shaped ; anthers rather protruding ; 

 stigma clubbed ; berry four-celled ; seeds immersed 

 in pulp. This genus is nearly allied to gardenia, and 

 is treated in the same way. In their native country 

 they yield eatable fruit, but it is not much esteemed. 



GENISTA (Linnaeus). An extensive genus of 

 evergreen, and deciduous, some of them creeping 

 shrubs, and chiefly European. The flowers are mo- 

 nadelphou?, and belong to the natural order, Legn- 

 mino&a. The greater number of them were known 

 by the common English name broom, so useful to the 

 tidy housewife, to the dyer, and to the brewer, before 

 hoos were substituted. See SEEDS. 



GENTIAN A (Linnaeus). A very numerous genus 

 of herbaceous plants, valued for their dwarf-habit and 

 beautiful flowers. They are pentandrious, and give 

 a title to one of the natural orders, viz., Gentianece. 

 They succeed pretty well in any light, rich soil, or 

 moor earth ; some of them require to be kept in pots 

 during winter, that they may have the protection of 

 a frame. 



GENTIANECE. A natural order, containing 

 twenty-two genera, of which there are a great many 

 species. The gentians, which are the type of the 

 order, are mostly dwarf herbaceous plants, with deep 

 blue, and different shades of orange flowers. They 

 are all pretty, and some of them extremely 

 beautiful, though the most of them are difficult of 

 cultivation. The Chironias, Erythrceas, Spigelias, and 

 Menyanthus, are all interesting families, and highly 

 regarded by all lovers of plants. Some of the gen- 

 tians are medicinal, containing an extremely bitter 

 principle, of which the Villarsias, Chirayitas, and 

 Waltens, partake, but in a weaker degree. The root 

 Spigelia Marylandica is infused in wine as a febrifuge, 

 and in water as a vermifuge. 



Collectively considered, the Gentianece are hypo- 

 corollous Primulacca;, with opposite, simple, regular 

 flowers; stamens alternate, with the lobes, and the 

 germen superior, and formed of two carpels. The 

 leaves are opposite, rarely compound, sessile, or 

 petiolate, and destitute of stipules. The outward 

 symptoms sometimes observed to follow the ad- 

 ministration of what has been supposed to be 

 gentian, have proved to be owing to the Veratrum 

 album, which grows in the same districts, having been 

 collected for it in mistake. The base of the famous 

 Portland powder is said to be gentian. 



GEODORUM (Jacquin). An elegant flowering 

 genus belonging to the Orchidece. Generic charac- 

 ter ; sepals spreading, the lower one longest and 

 broadest ; labellum hollow and swollen, not jointed 

 at the base ; column freely jointed, apex obtuse ; 

 masses of pollen in two lobes ; glands united. 

 These curious plants are grown in pots of sandy loam 

 and moor earth, and do better in a frame in summer 

 than in the hot-house. They were called Limodorum 

 by Roxburgh and other botanists. 



GEOLOGY, the science which treats of the struc- 

 ture of our globe ; its compound title being derived 

 from two Greek words, implying a Discourse on the 

 Earth. Some modern writers have employed the 

 term " geognosy" as descriptive of this science ; but 

 it will be obvious that the knowledge o the earth 

 which is here implied, can hardly be satisfactorily 

 conceded to observers who have scarcely penetrated 

 its crust. We prefer, therefore, the less assuming 

 title placed at the head of this article for presenting 

 our account of the labours of those persons who have 

 distinguished themselves in this branch of science, 

 referring our readers to the articles ALLUVIAL, DI- 

 LUVIAL, STRATA, &c., for a view of the separate 

 details, which would otherwise swell this article to 

 an inordinate length. 



It is natural that man should feel a deep interest 

 in the history of the globe on which he is placed, 

 and, indeed, we find that theories for illustrating the 

 structure of the earth, and explaining the changes it 

 has undergone during the lapse of ages, are as old, 

 if not older, than any that are to be found for illus- 

 trating any other branch of natural history. But the 

 geologist of the olden time, unfortunately, commenced 



