ANANAS. 



[ 33 ] 



ANDR^ACE^. 



That internal reflexion, however, is not 

 the cause of the separation of the colom^ed 

 rays, is shown by the fact that those lateral 

 surfaces of crystals which, when ^dewed 

 through the microscope (with the polarizer 

 and plate of selenite alone), appear of a cer- 

 tain colour, say green, exhibit the comple- 

 mentary tint, red, when viewed with the 

 naked eye from the side of the stage ; hence 

 the two coloured rays are separated merely 

 by refraction. 



The margins of cavities containing air and 

 air-bubbles, which sometimes exist in the 

 crystals, exhibit the colours in the same 

 manner and from the same cause as the 

 lateral oblique surfaces of the crystals. 



Nothing can surpass the curious and beau- 

 tiful appearance presented by analytic cry- 

 stals ; the delicacy and brilliant transparency 

 of their colom'ed margins giving them the 

 aspect of figures drawn with coloured ink. 

 PI. 7. fig. 11 «j b, represent two crystals 

 of nitre, viewed with the polarizer but nei- 

 ther the analyser nor the plate of selenite ; 

 fig. 12, a, b, represent two crystals as seen 

 when the polarizer and plate of selenite are 

 used, exhibiting the complementary colom's; 

 fig. 12 c, represents an air-bubble enclosed in 

 the crystal. See Dichroism and Polar- 

 ization. 



BiBL. Brewster, Phil. Trans. 1835; Fox 

 Talbot, /. c. 1837. 

 ANANAS. See BROMELiACEiE. 

 ANAULUS, Ehr.— A genus of Diato- 

 maceae. 



Char. Frustules single, compressed, sub- 

 quadrate, not furnished with either tubular 

 processes, nodules or apertures, but having 

 lateral constrictions. 



In the latter character it resembles Bid- 

 dulphia. 



Kiitzing admits one species : — 

 A. scalaris, Ehr. Valves turgid in the 

 young state, very broad and flat when ma- 

 ture; having 4, 6, 8, or 14 lateral constric- 

 tions, which give the front view a ladder- 

 like appearance ; marine; diameter 1-470 to 

 1-175". 



Found in the Antarctic Ocean. 

 A. indicus, Ehr. = Terpsinoeiudica, Kiitz. 

 BiBL. Ehrenberg, Bericht. derBerl. Akad. 

 1844, p. 197; 1845, p. 361; Kiitzing, S^ec. 

 ^^^r. pp. 119, 120. 



ANCHORELLA,Cuv.— A genus of Crus- 

 tacea, of the order Siphonostoma. 



Char. Body short, produced in front into 

 a kind of neck, which is transversely rugose ; 

 arms two, furnished with a sucker or adhe- 



sive disk at the end, and confluent through- 

 out their length. 



Two British species : — 



1. A. uncinata (PI. 14. fig. 7), milk- 

 white ; found on the gills and gill-covers of 

 the cod, haddock and whiting ; length about 

 1-2". ^ 



2. A rugosa, found on a species of cod ; 

 length about 1-3". 



The above characters refer to the female. 



BiBL. Baird, Brit. Entomostraca, p. 336. 



ANCYRIUM, Werneck.— A genus of Po- 

 lygastric Infusoria, according to the system 

 of Ehrenberg. 



Char. That of an Enterodelous Bodo, with 

 a moveable setaceous foot. 



6 (?) species. 



BiBL. Werneck, Bericht. d. Berlin. Akad. 

 1841, p. 377. 



ANDR.EA, Ehrh.— A genus of Mosses. 

 See Andr^ace^. 



ANDRiEACE^.— A family of inopercu- 

 late Acrocarpous (terminal-fruited) Mosses, 



Fig. 11. 



Andreea rupestris. 



Fig. 10/ A sporange not }'et open. 



Fig, 11. A sporauge burst into four valves, united at their 

 points. Magnified 20 diameters. 



characterized especially by the peculiar mode 

 of splitting of the fruit, somewhat analogous 

 to that which is found in Jungermannia, the 

 urn-shaped capsule dividing perpendicularly 

 when ripe into four or eight valves, which 

 remain attached together at their points 

 (figs. 10 and 11). Man}^ of the species have 

 the leaves of a dull brownish colour. The 

 cells of tissue of the leaves are parenchyma- 

 tous, with their walls thickened, and they 

 are somewhat papillose on the surface. The 

 calyptra at first covers the capsule entii*ely, 

 then splits off' horizontally as a mitre-shaped 

 or bell-shaped cup, which is very fugacious. 

 The archegonia and antheridia are either on 

 the same or distinct plants (monoecious or 

 dioecious), and the latter terminal on distinct 

 branches. The few British species are na- 

 tives of rocky, usually alpine districts, and 

 constitute the only genus, Andrcea. 



D 



