MACROTHRIX. 



[ 487 J 



MAIZE. 



-v. 109 ; Cunningham, Mic. Exam, of Air, 

 Calcutta, 1873. 



MAC'ROTHRIX, Baird. A genus of 

 Entomostraca, of the order Cladocera and 

 family Daphniadas. 



Char. Five pairs of legs ; beak directed 

 forwards ; superior antennae of considerable 

 size, one-jointed, and pendulous from the 

 beak ; interior antennae two-branched, pos- 

 terior branch four-, anterior three- jointed, 

 and with a very long filament arising from 

 the end of the first joint ; a .black spot at 

 the root of the superior antennae. 



M. laticornis (PI. 19. fig. 25). Shell 

 oval, smooth, anterior margin strongly 

 ciliated ; eye areolar. 



Found in ponds. 



M. roseus. Eye without an areola ; 

 superior antennas longer and more slender 

 than in the above. 



Probably a variety of the last. Found 

 in Scotland. 



BIBL. Baird, .Br. Entom. 103; Norman 

 & Brady, Mon., Nat. Hist. Tr. Northumb. 



MAJDOTHE'CA, Du- pj^ 441 

 mortier (Jungermannia, 

 L.). A genus of Jun- 

 germannieae (Hepaticae), 

 containing two British 

 species: one, M. platy- 

 phylla (fig. 441), com- 

 mon on walls, rocks, and 

 trees ; the other, M. Ice- 

 vigata, found on alpine 

 rocks. The sporange is 

 borne on a short stalk, 

 globose, and bursts by 

 four convex valves, from 

 which the elaters are 

 quite free. The globose 

 persistent epigone is seen 

 in the figure inside the Madothecaplatyphylla, 

 two-lipped perigone. Magn " 5 dmm8 ' 



BIBL. Endl. Gen. Plant. Suppl i. 1341 j 

 Hooker, r. FL ii. 125, JSrit. Jungermann. 

 pis. 35, 40, and Supp. pi. 3 ; Ekart, Synops. 

 Jungerm. 52, pi. 3. fig. 24, pi. 6. fig. 44. 

 MAGNESIA, SALTS OF. 

 Ammonio-phosphate of magnesia or triple 

 phosphate. This salt is frequently met with 

 in animal secretions which have undergone 

 decomposition, also in calculi. The most 

 common forms are prismatic, and figured in 

 the group a, b, PI. 13. fig. 1 j but their va- 

 rieties are endless. Those of the above 

 group are frequent in decomposing urine, 

 blood, faeces, &c. Those in group c are 

 occasional in urine. Those of group d are 



found in the contents of the vesiculge semi- 

 nales. The forms e and /are rare. Fig. 2 

 a, b, represents the so-called penniform 

 crystals, or rather groups of crystals (prisms) 

 occasionally found in urine. Fig. 3 repre- 

 sents the stellate form, occasionally found 

 in urine; sometimes the minute and imper- 

 fectly formed crystals of fig. 4 are met with 

 in the same liquid. 



The crystals belong to the rhombic system. 

 The prismatic crystals were formerly re- 

 garded as consisting of a neutral, and the 

 feathery of a bibasic salt ; but the composi- 

 tion of the two is the same, and the variation 

 in form depends upon the conditions under 

 which they are produced. 



The prismatic forms may be prepared by 

 allowing urine to decompose spontaneously, 

 or by diluting this secretion with water and 

 gradually stirring-in very dilute solution of 

 ammonia in small quantities at a time j the 

 penniform crystals by adding excess of solu- 

 tion of ammonia to very dilute solutions of 

 the phosphate of ammonia and sulphate of 

 magnesia ; and the feathery forms by adding 

 excess of ammonia to urine. The prismatic 

 crystals form a beautiful polarizing object. 

 Sulphate of magnesia (Epsorn salt). When 

 crystallized upon a slide from an aqueous 

 solution, the prisms of this salt, mounted 

 in balsam, form an interesting polarizing 

 object ; they are also analytic. 



or ate of magnesia fused into a bead 

 before the blowpipe is a beautiful obiect 

 (Sorby). 



Urate of magnesia. See UBIC ACID. 

 BIBL. That of CHEMISTRY, and Phil. Mag. 

 1852, iii. 373. 



MAG'NETITE. See ROCKS. 

 MAGNIFYING POWER. See MEA- 

 SUREMENT. 



MAGOSPH^ERA, Haeckel. A genus of 

 Catallacta (Protista) ; according to Kent, a 

 Flagellate Infusorian. 



BIBL. Haeckel. Jenai. Zeit. 1870 ; Kent, 

 Inf. 323. 



MAHOGANY. The wood of various 

 species of Swietenia (Nat. Ord. Cedrelaceaa). 

 Cross sections' of this well-known wood 

 form good objects for showing the structure 

 of WOOD with low power. 



MAIZE. Indian corn, Zea Mays, L. 

 One of the family of Grasses producing 

 seeds used as corn. The seeds, or rather 

 caryopses, are remarkably firm, being of a 

 horny texture in the outer part of the sub- 

 stance, while the central mass is more cr 

 less brittle nnd soft. The solidity of the 



