GUM. 



[ 300 ] 



GYRINUS. 



G. orbicularis, Hmpe.= Gnwmm orbicu- 

 laris, Br. Eur. 



G. riparia= Cinclidotus riparia, Wils. 



G. fontinaloides (figs. 293-5) = Cincl. 

 fontinaloides, P. B. 



GUM. A name applied to various viscid 

 (not oily) secretions of plants. Gums have 

 no microscopic structure when pure and 

 clean, but often exhibit under the microscope 

 traces of structures, such as debris of cellular 

 tissue, filamentous Fungi, &c., which have 

 become imbedded in them while soft. Gum- 

 arabic has been used sometimes for mounting 

 objects, in the same way as Canada balsam, 

 but it is not a satisfactory material. Sections 

 of very soft tissues or very minute objects may 

 be made by imbuing them with or immersing 

 them in solution of gum and allowing the 

 whole to dry up to a tough, semisolid mass, 

 capable of being sliced with a razor. The 

 slices are freed from gum by soaking in water. 



GUTTA-PERCHA. A kind of gum-resin 

 produced by the evaporation of the milky 

 juice of the Isonandra gutta, one of the 

 family of the Sapotaceae, a native of Sumatra 

 and the neighbouring regions. Its relation 

 to the microscope arises from its use in a 

 solid form and as cement, in mounting mi- 

 croscopic objects in cells. See CEMENTS 

 and PREPARATIONS. 



GYGES, Bory. Described by Ehrenberg 

 as a genus of Volvocineae, having neither 

 eye-spot, tail, nor flagelliform filament ; the 

 carapace(cell-membrane) simple, subglobose. 



Motion very slow. He gives two species : 



G. granulum (PI. 41. fig. 14). Ovate or 

 subglobose, internal granular mass dark 

 green; diam. 1-1150". Aquatic. 



G. bipartitus. Nearly spherical, internal 

 mass yellowish-green, frequently bipartite; 

 diam. 1 -480". Aquatic. 



So far as appears from the descriptions 

 and figures, these do not seem to differ from 

 PROTOCOCCUS. 



(For G. sanguineus, Shuttleworth, see 

 RED SNOW.) 



BIBL. Ehr. Infus. p. 51. 



GYMNOGONGRUS, Mart. A genus of 

 Cryptonemiacese (Florideous Algae), with 

 horny branched fronds, the divisions cylin- 

 drical or compressed, a few inches high, of a 

 purplish-red colour. The substance of the 

 branches presents three layers of closely- 

 packed filamentous cells, the central longi- 

 tudinal, the intermediate curved, and the 

 peripherical horizontal and monilif orm . The 

 spores have not been observed; the tetra- 

 spores (cruciate) are arranged in monili- 



form rows, in wart-like thickenings of the 

 branches. 



BIBL. Harvey, Brit. Mar. Alg. p. 145. 

 pi. 18 B ; Engl. Bot. pi. 1089 & 1926. 



GYMNOGRAMMA, Desv. A genus of 

 exotic Gymnogrammeae ( Poly pod aeousFerns ), 

 some of the species of which are remarkable 

 for a yellow or white pulverulent appearance 

 on the back of the fronds, owing to the 

 presence of abundance of microscopic cellu- 

 lar hairs, ex. gr. G. Calomelanos, G. chryso- 

 phvlla, ochracea, &c. 



GYMNOGRAMMEJE. A. sub-tribe of 

 Polypodaeous Ferns, containing several in- 

 teresting exotic genera. 



I. GYMNOGRAMMA. Sori on the backs 

 of all the veins and venules. Veins pinnate 

 or forked, scarcely anastomosing. 



II. HEMIONITIS. Sori on the backs of all 

 the veins and venules. Veins very much 

 branched, anastomosing in more or less 

 regular meshes. 



III. ANTROPHIUM. Sori imbedded in the 

 back of all the veins and venules. Veins 

 very much branched, anastomosing in more 

 or less regular meshes. 



GYMNOMITRIUM, Corda. A genus of 

 Jungermannieae (Hepaticaceae), containing 

 one British alpine species, the Jungermannia 

 concinnata of the British Flora. 



BIBL. Hook. Brit. Jungerm. pi. 3; Ekart, 

 Synops. Jungerm. pi. 8. fig. 63; Engl. Bot. 

 pi. 1022. 



GYMNOSPERMIA. A division of the 

 Flowering Plants (see VEGETABLE KING- 



DOM),includingtheCoNIFER^E,GNETACE^E, 



and CYCADACE^E ; deriving this name from 

 the mode of development of the OVULES. 



GYMNOSPORANGIUM, D. C. A 

 genus of Cseomacei (Coniomycetous Fungi, 

 see also UREDINEI). G. Juniperinum grows 

 upon living branches of the common Juniper, 

 appearing at first like an exanthema on the 

 bark, which in wet weather swells up into an 

 orange-coloured tremelloid, plicate mass, 

 which readily dries up, however, and then is 

 scarcely visible. Somewhat rare, but when 

 present generally copious. 



BIBL. Berk. Brit. Flora, vi. part 2. 

 p. 361 ; Fries, Syst. Myc. iii. p. 505. 



GYMNOSTOMUM, Schwagr.A genus 

 of Mosses, now distributed into PYRAMI- 

 DIUM, PHYSCOMITRIUM and other genera. 



BIBL. Miiller, Syn. Muscorum ; Bruch 

 and Schimper, Bryologia Europeea. 



GYRINUS, Geoffr. A genus of Coleo- 

 pterous insects, of the family Gyrinidae. 



G. natator, one of the eight British spe- 



