DESMIDIEJS. 



DEVONIAN SYSTEM. 



than M small shallow pool* which do not dry up in 

 Mr. Mr. Raid ay, however, that the luiue species never 

 occur in the same pools two you* in succession. They prefer open 

 noon and exposed places, and arc rarely found in woods, shady 

 places, or deep ditches. They kre seldom found in turbid water of 

 any kind. In this respect they are the opposite of their congeners 

 the IKatumaai* which almost as a rule are found where the Iktmidivt 

 are not 



The best way of procuring then) for examination is to take a 

 piece of linen, lay it on the ground in the form of a bag, ami then, 

 by the aid of a tin box or ladle, scoop up the water, and strain it 

 through the bag. After this process has been repeated a few times, 

 the specimens of Dtimidiea will be found in great almiulmice on the 

 linen, which, if kept moist, will allow of the growth and develop- 

 ment of these beautiful objects for many months. 



The stuily of this family will undoubtedly amply repay the 

 naturalist for years to come. Comparatively little is known of the 

 species beyond the continent of Europe. The following is an analysis 

 of the genera found by Mr. Haifa in the British Islands : 



* 



Plant an elongated jointed filament. Sporangia orbicular, smooth. 



1. JUyalolkeca. Filament cylindrical. Two species. 



2. lHdymopr\m. Filament cylindrical, or sub-cylindrical. Joints 

 with two opposite or dentate projections. (Kg. 1.) Two species. 



8. Itrtmidium. Filament triangular, or quadrangular ; joints con- 

 nected by a thickened border. Two species. 



4. Aptogonum. Filament triangular or plane, with foramina 

 between the joints. One species. 



5. Sflurmoima. Filament plane, margins incised or sinuated ; 

 joints with junction-glands. Two species. 



* 



Frond simple from complete transverse division, distinctly con- 

 stricted at the junction of the segments, which are seldom longer 

 than broad ; sporangia spinous or tuberculated, rarely if ever smooth. 



6. MicnutrHau.Lobef of the segments incised or bidentate. 

 (Kg. 2.) Thirteen species. 



7. nattritm Segments sinuated, generally notched at the end, 

 and with inflated protuberances. (Pig. 8.) Eighteen species. 



8. Cotmarium. Segments in front view neither notched nor 

 inuated ; in end view elliptic, circular, or cruciform. Thirty-three 



9. Xantkulitu*. Segments compressed, entire, and spinous. (Piyt. 

 4 and 5.) Six species. 



10. Arthrodetmiu. Segments compressed, and having only two 

 spines or mucroa. Two species. 



11. .SravnufniM. End view angular, radiate, or with elongated 

 processes which are never geminate. Forty species. 



12. IHdymoeiadon. Segments angular, each angle having two 

 processes, one inferior and parallel with the similar one of the other 

 segment, the other superior and divergent One species. 



Frond simple, from complete transverse division, generally much 

 elongated, never spinous, frequently not constricted at the centre. 

 Sporangia smooth. 



13. Tctmemonu. Frond straight, constricted at the centre, and 

 notched at the ends. Three species. 



14. PtniuM. Frond straight, scarcely constricted at the centre. 

 Right species. 



15. Docidi**, Frond straight, much elongated, constricted at the 

 centre, truncate at the ends. Seven species. 



1. dostsHsm. Frond crescent-shaped or arcuate, not constricted 

 at toe centre. (Pig. 6.) Twenty-two species. 



17. Spintmia. Frond straight, not constricted at the centre; 

 endochrome spirally twisted. Two species. 



Cells elongated, entire, fasciculated. 



18. Amtitlro,lam<u. Cells aggregated into faggot-liko bundles. 

 (Pig. 9). One species. 



Frond composed of few cells, definite in number, and not funning a 

 filament. (Sporangia unknown). 



1. Ptduuhmm. Cells arranged in the form of a flattened star, 

 their outer margin bidentato. (Piyt. 7 t 8.) Eleven species. 



SO. StaudeuHU. Cells oblong or fusiform, entire, placed side by 

 aid* In a single row, but during division into two rows. Six species. 



( Ital/s and Jenner, IlritiA Itetmuiinr ; Siebold, O Vnif,IMar Plant, 

 mmdAnimaU, in Hie. Jonrna/,-1858 ; Meneghini, On Ike Animal Naturr 

 t MatoMcwc, translated by Ray Society, 1864; A. Kraun, On 

 Ac/MMMMOMf m tkt Plant , translated by Ray Society, 1854 ; Liudley. 

 P*fflUf Kingdom; Nageli, Utt*ngt tinuUigtr Atgtn pkytiologitck 

 mmd i&rmaHKu iewMM, Zurich, 1848; Cohn, On Ike Natural 

 vtoCTWou plnnalit, translated by Ray Society, 1864.) 



DKSMol'H Y'LLUM, a genus of Fossil Kadiate Animals belonging 

 to the Zoonhites found in the London Clay of Shepiwy. (' UeoL 

 Trans.,' N. 8., voL v. t 8, f. i.) 



HKSVAUXIA'CE.K, Jtrutltmrtt, an obscure and little known 

 natural order of Plants, consisting of a few Australian sedge-like 

 herbs, of no known utility. They are nearly related to Katiatttc and 

 Kriocaulattfr, and are principally charaterised among other Olnmoa* 

 Kndogens by having several carpels placed in the middle of each 

 flower. The most reoent character is the following, given by Kn.llii-lu-r 

 in his ' Genera Plautarum ' : 



Dwarf Australian herbs with the appearance of a pigmy Cypertu 

 or Seirptu ; the roots fibrous or fasciculated. Culms filiform, undi- 

 vided, leafless. Leaves radical, between thread-slia]>d and bristly, 

 sheathing at the base. Spikelets hermaphrodite, in two ranks, 

 1 -flowered, or terminal and solitary with one or many florets. Ulume 

 single, anterior, or two nearly opposite each other, coarse. Palest 

 none, or delicate, single or double, parallel with the glumes. Stamen 

 single, anterior. Filament filiform, simple. Anthers turned inwards, 

 1-celled, attached by the back above the base. Ovary either single 

 and sessile (we would exclude this character) or several attached to a 

 common axis at different heights, imbricated downwards, 1-celled. 

 Ovule solitary, suspended from the apex of the ovary, orthotropous, 

 with the foramen regarding the base of the ovary. Styles filiform, 

 simple, united to each other at the base. Stigmas simple, or with a 

 feathery beard. Utricles membranous, dehiscing lengthwise at the 

 side. Seed orthotropous, pendulous; skin leathery and rather hard. 

 Albumen fleshy and abundant Embryo antitropous, lenticular, 

 applied to the albumen at the extremity of the seed opposite the 

 umbilicus ; the radicular extremity papillose, and regarding the base 

 of the fruit (' Genera Plantarum,' p. 119.) 



There are 4 genera and 15 species in this order. 



DETRITUS and DEBRIS, two words now universally received 

 into the language, the former of Latin, the latter of French origin. 

 They are very frequently employed in works of geology and p!i 

 geography, when treating of the formation of alluvial deposits. By 

 Debris, in geological language, is meant generally the fragments of 

 rocju, boulders, gravel, sand, trunks of trees, carcasses of "limal^, tc., 

 detached from the summits and sides of mountains by the effect of 

 the elements, or resulting from sudden convulsions at the surface of 

 the earth. By Detritus we understand the some Debris finely com- 

 minuted or pulverised by attrition. Debris in general comprises 

 Detritus ; but Detritus excludes the idea of the larger Debris. 



Modern Debris seldom extends beyond the foot of the mountains 

 whence it is derived, the channels of torrents, and the higher parts 

 of the beds of rivers; Detritus alone, except in the case of such 

 tilings as float, being carried down to the mouths of large streams. 

 The boulders which lie strewn over such great extents of laud, ami 

 which are found at great depths below the surface-soil, together with 

 fossil-trees, bones of animals, to., are the Debris of a former age, no 

 cause now in action being apparently capable of bringing them to 

 such distances from their original sites. 



DEUTZIA, a genus of Plants belonging to the natural order 

 Philadelphafc<r, inhabiting the North of ludia, China, and Japan. 

 The tube of the calyx is campaniilate, tomentose, the limb 5- or <!- 

 cleft. The petals 5 or 6, and oblong. The leaves are opposite, 

 petiolate, ovate, acuminated, serrated, wrinkled, and veined. 



J>. icabra has its leaves covered with stellate siliceous hairs, which 

 makes them very rough, and renders them of use to cabinet-makers 

 as polishing agents. The siliceous bodies are beautiful objects vi. . .1 

 by reflected light under the microscope, 



DEVIL IN A BUSH, 1 Vulgar names of the genus Niydla. 



DEVIL IN A MIST, / [NioM.LA.1 



nr.VlL'S APPLE. [MANDBAOOIIA.] 



HKVII.'S BIT, the vulgar name of .Scooiom tucciia. [SCABIOSA.I 



DKVII.'S LEAF. [URTICA.] 



DEVONIAN SYSTEM. A great portion of the Palicozoic Strata 

 of North and South Devon has been thus termed by Sedgwick and 

 Murchison (' Qeol. Trans.'), and also referred to as of coeval formation 

 with the Old Red-Sandstone of Herefordshire. Further investigation 

 ha* shown that a portion of the strata in North Devon belongs to the 

 Carboniferous System, and is equivalent to the lowest shales and 

 sandstones thereof. The Old Red-Sandstone must certainly be admit tl 

 to be coeval with some parts of the Devonian Strata, which besides 

 contain several red-sandstone members ; but there is reason to think 

 that the true place of much of the stratification of South Devon, on 

 the ordinary geological scale, is rather about the upper part of the 

 Old Hed-Sandstone ; and this mode of viewing these rocks harm 

 with the distribution of organic remains in the Silurian, Devonian, 

 and Carboniferous Deposits. 



The following table by Professor Sedgwick gives at one view the 

 relation of the rocks which enter into the composition of the Devonian 

 Formation: 



Lower or Plymouth / Dartmouth Slate, Plymouth Limestone and 

 Oroup. \ Ited ( irit. and Lixkeard Slate. 



Middle or Caithness f Hereford Sandstone, Marl, and Coriutone, 

 Oroup. Dipterous Flag. 



Upper or Petherwin f Petherwin Slate and Clymonia Lim 

 Uroup. I Marwood Sandstone. 



