

ONAPHALIUM. 



GNETACE^E. 



1053 



GNAPHA'LIUM (from yrtC^wAor, which signifies the wool which 

 the fuller cut* off in fulling tlie cloth), genus of Plants belonging 

 to the natural order Cbmpotidr, to the sub-order Corymliiferte, the 

 tribe Smefumidnr, the nub-tribe Gnafkalita, the division llclichrytea. 

 It has the ray-florets pistilliferous, the centre with both stamens and 

 pistils, all of them tubular; the pappus capillary ; the receptacle 

 flat, naked ; the involucre hemispherical, imbricated ; the scale* 

 equalling the floreU, but not mixed with them. The corolla of the 

 outer florets is often obsolete. The species of this genus have a soft 

 pubescent foliage with dry flowers, which' keep for a long time 

 without perishing, and like those of some ajiecics of llelirhrytum 

 and Xerantkemum, are called ' everlastings ' or 'immortal' flowers. 

 The species are numerous. Five are British. Of these (J. tjiginonm 

 is the most common, growing in wet and sandy places. G. lotto- 

 adimm. O. tytratieum, 0, mpinum, and (!. jiwillum are all rare plants. 

 Several of the species of the old genus Gnaphalium are referred to 

 new genera as Anttnnaria and Filayo. Q. tlioicum is Antennaritt 

 dioiea of Gjcrtner. It grows on mountain heaths in Great Britain, 

 and is commonly called Cotton-Weed, and by the older herbalists res 

 Cati. IU flowers were admitted into the older pharmacopoeias under 

 the name of ' Flores hispiduli Pes Cati.' They are astringent, and were 

 employed in the cure of hooping-cough, phthisis, and haemoptysis. 

 U. amarium (lldichryium arenarium) has been employed as a remedy 

 in dyspnoea. Q. Stcrchat of Linnaeus, Goldilocks, the JJtlichiytum 

 StcreJuu, is mentioned by Theophrastus ('Hist PL' 9, 21). The 

 flowers of this plant were formerly much used in medicine, but are 

 seldom employed at the present day. 



(Babington, Manual of Brititk Botany ; Burnett, Outline* of Botany; 

 Fraas, Synoptit Plant. PL Clauicte.) 



GNAT. [CcuciDES.] 



GNATHODON, a genus of Conchiferous Molliuca with the 

 ligament inclosed in the cartilage pit, established by Dr. Gray. This 

 peculiarity of structure is also found in a new genus Mu/inia. 



GNATHO'STOMA (yviiios, a jaw, and a-r&tia., the mouth), a genus 

 of Nematoid i'ntoioa [ENTOZOA], discovered by Professor Owen in the 

 stomach of the tiger. These worms, the largest of which are about 

 an inch in length and a lino in diameter,' were found in the substance 

 of several small cellular tumours situated immediately beneath the 

 mucous membrane of the stomach, and apparently formed by the 

 condensation and thickening of the submucous cellular tissue, which 

 was probably owing to the irritation of the EiUozoa. Only a pair of 

 then timl was found in each tumour, and they always consisted of 

 male and female, the former of which was about one-fourth smaller 

 than the latter. 



In both sexes the body is round, elastic, and attenuated at both 

 extremities ; the tail is more obtuse and bent in the male ; the head 

 U obtuse and truncated in both of them. The integuments ore trans- 

 parent, and, from the intestinal and genital tubes showing through 

 the surface of the body, appear to be striated transversely. The 

 anterior two-thirds of the body are covered with a circular series of 

 minute reflected spines, each furnished with three points. The mouth 

 is surrounded by a tumid circular lip, and armed with several rows 

 of spinous processes of a similar structure to those on the body. The 

 orifice of the mouth itself is bounded on each side by a jaw-like pro- 

 ceat (whence the name of the genus), the anterior margin of which is 

 formed into three straight horny points, or processes, directed for- 

 wards. The male organ of generation consists of a slightly-curved 

 slender spiculuui, not furnished with a sheath as in the Stronyyliu, 

 and surrounded by eight distinct pointed papillic. 



The most interesting point in the internal structure of this entozoon, 

 and which does not appear to have been hitherto detected in any other 

 animal of this class, is the existence of a distinct salivary apparatus, 

 similar to what is found in the J/ololliuria and other Echinodermata. 

 " This apparatus," says Professor Owen, " consists of four elongated 

 straight blind tubes, each about two lines in length, which are placed 

 at equal distances around the commencement of the alimentary canal, 

 having their smaller extremities directed forwards, and opening into 

 the mouth, and their closed obtuse ends passing backwards into the 

 abdominal cavity. When examined with a lens of a quarter of an 

 inch foctw, the parietes of these salivary tubes present very distinct 

 oblique or spiral decussating fibres ; their contents are semi-pellucid 

 in the recent worm, but become opaque in spirit of wine." The 

 existence of this salivary apparatus along with the more perfect 

 organs of mastication, as the jaws, in this cntozoon U highly interest- 

 ing, as it shows an approximation to the structure of the digestive 

 organs in the higher classes of MijtpiQ., 



Professor Owen has since found the (tnaihottoma in the stomach of 

 other animals of the Cat kind, as the leopard. 



Beautiful preparations of both the male and female worms dis- 

 sected are preserved in the museum of the College of Surgeons in 

 London. 



( ; X K I ss, a German term for the lowest series of stratified primary 

 roclu, the introduction of which marks the obligations which British 

 geologist* owe to the school of Werner; while such tern as lias, 

 cornbrash, gault, Ac., record the original discoveries of Smith and 

 oUur English writers. As there are no organic remains in the gneiss 

 strata, and the variations of its composition and structure appear 

 independent of ths relative antiquity of the deposits, it is impossible, 



except by the help of the included limestones, quartz-rock*, clay-slates, 

 Ac., even to attempt the division into formations of the vast thickness 

 of the gneiss strata which appears in the Highlands of Scotland, the 

 mountains of Scandinavia, Ac. 



Gneiss is generally a compound of the same three minerals as 

 granite, namely, quartz, felspar, and mica. In the same manner as 

 granite varies in the proportion of its ingredients, the magnitude of 

 the component crystals, the absence of mica, or the substitution of 

 other minerals for it, so gneiss exhibits corresponding variations. 



Dr. M'Cullooh, whose examination of the gneiss tracts of Scotland 

 was very complete, presents an extended synopsis of the varieties of 

 gneiss which he had observed. His table includes indeed a great 

 number of mineral compounds different from the general char.i 

 gneiss, but is nevertheless valuable to the geologist He con-i I.T.- 

 gneiss in three divisions : first, of regular composition, containing at 

 least three of the four minerals quartz, felspar, mica, and hornblende ; 

 secondly, of irregular composition, containing compact felspar ; and 

 thirdly, of irregular composition in other respects. ('Treatise on 

 Hocks.') 



The following U a synopsis of the first division : 

 Granitic Gneiss. This U always large grained. 

 a. Composed of quartz, felspar, and mica. 

 6. Composed of quartz, felspar, and hornblende, 

 c. Composed of quartz, felspar, mica, and hornblende. 

 Schistose Gneiss. The structure is foliated like mica-schist, or 

 granular like quartz-rock. 



a. Composed of white felspar and quartz in minute grains 



with rare scales of mica (resembles quartz-rock). 

 I. Composed of felspar and quartz as above, but with abund- 

 ance of mica (so as to resemble mica-schist). 



c. In this the mica is extremely abundant, so as to form 



continuous lamina. 



d. In this the mica is predominant, and there are large inter- 



spersed crystals of felspar. 



e. Composed of large grains of quartz and felspar with little 



mica. 



Laminar Gneiss. Each substance occupying a distinct Km ill, 

 a. Composed of quartz and felspar. 

 6. Composed of quartz, felspar, and mica. 



c. Composed of quartz, felspar, and hornblende. 



d. Composed of felspar and hornblende. 



e. Composed of quartz, mica, and hornblende. 



All the varieties of rock comprised under the title of gneiss are 

 stratified, the beds varying much in thickness, and being most 

 remarkably subject to contortions both on a large and small scale, 

 especially where granite veins cross the lamina;. 



Gneiss is an interesting rock for study to the English geologist 

 Over a considerable portion of the mainland, and in the western 

 islands of Scotland, gneiss is the predominant and fundamental 

 rock. It is also found abundantly in Ireland, The picturesque 

 features of gneiss present almost every imaginable variety, a broad 

 expanse occupied by this rock sometimes extending over considerable 

 tracts, and being only relieved iu its savage monotony by occasional 

 pooh) of water or patches of bog ; while in other districts it forms 

 wild and rugged hills, assuming a mountainous character, and 

 displaying broken and craggy faces of rock. (Ansted.) 



Gneiss admits of considerable variety by the substitution of other 

 minerals for either the quartz, felspar, or mica of which it is ummlly 

 composed. The mica, for instance, may be replaced by talc, forming 

 what is called Stratified 1'rotogine. In some cases hornblende is 

 superseded to the ordinary materials, forming a syenitic gneiss. 



GNETA'CE^S, Joint-Fin, a natural order of Plants belonging to 

 the small class of Gymuosperms. The species consist of small trees 

 very much branched, or of sarmeutose shrubs with opposite or 

 clustered branches, and thickened separable articulations. The leaves 

 are opposite, entire, with pinnate veins, sometimes very minute and 

 scale-shaped. The ligneous tissue of the wood is marked with 

 circular discs. The flowers are monoecious or dioecious ; the stamens 

 are contained in a 1 -leaved calyx; the ovary is perforated at the 

 apex, containing in a single cavity a solitary erect ovule ; the ovule 

 pointed by a style-like process, formed from the membrane of the 

 nucleus ; there is no trace of a style or stigma. 



This small order of plants has been formed by Blume, whose 

 memoir in the ' Aunales des Sciences Naturclles ' contains the prin- 

 cipal knowledge we have of this order. "This little family, he 

 says, " constitutes a part of that natural class of vegetables in which 

 the fertilisation of the ovule takes place immediately, without the aid 

 of style or stigma, through the foramen of the ovule itself. Through 

 Ejihrdra, which has hitherto been placed with font/era 1 , the order is 

 closely connected with the latter : and, on the other hand, it tends 

 towards Canarinacea, plants of a higher degree of organisation ; 

 since Gnetacea is beyond all doubt an instance of a more perfect 

 kind of evolution than either Coniferat or Cycadacea, From both 

 these orders (inttamt difler in the greater perfection of their sexual 

 organs, especially of their stamens; and at the same time their 

 ovules are not absolutely naked, but covered with a pericarpial 

 integument pierced at the summit. In the male flowers the perianth 



