MOULDS. 



[ 438 ] 



MOUTH. 



formed in one of the conjugating cells, with- 

 out transfer of contents, and this, germina- 

 ting in situ, breaks out from the parent-cell. 

 This account is probably correct as far as it 

 goes, but does not explain fully the develop- 

 ment of the spores. Hassall says the plants 

 are reproduced by zoospores ; this has been 

 confirmed by Kiitzing, who, together with 

 Itzigsohn, has observed the formation of 

 small rounded resting-spores in the joints, 

 which underwent segmentation and deve- 

 loped a number of smaller cells, the ultimate 

 fate of which was not observed. All this tends 

 to prove that the reproduction agrees with 

 that of Spirogyra, where we have 1. large 

 conjugation-spores, sometimes germinating 

 in situ, producing in some cases new fila- 

 ments, in others zoospores ; 2. zoospores 

 produced immediately from the contents; 

 and 3. what appeared to be encysted forms 

 of these (see SPIROGYRA). 



The only satisfactorily established British 

 species of this genus seems to be M. genu- 

 flexa, Ag. (fig. 139. p. 166). The cells are 

 about 1-720" in diameter in large specimens 

 (M. major, Hass.), and about three or four 

 times as long ; in smaller specimens (M. ge- 

 nuflexa, Hass., M. gracilis, Kiitz.) the dia- 

 meter is about 1-1200", the length of the 

 cells five or six times greater. The contents 

 of the cells, like those of MESOCARPUS, are 

 mostly evenly distributed. 



Mesocarpus notabilis, Hass. (Sirogonium 

 notabile, Kiitz.) is an obscure plant, perhaps 

 referable to this genus. 



BIBL. Vaucher, Conferees d'eau douce, 

 p. 79. pi. 8; Hassall, Brit. Fr. Alg. p. 171. 

 pi. 40 ; Kutzing, Sp. Alg. p. 43, Tab. Phyc. 

 v. pi. 1-3, and 36 ; Itzigsohn, Bot. Zeit. xi. 

 p. 681 (1853). 



MOULDS and MILDEWS. :These 

 names are generally applied indifferently to 

 a multitude of Hyphomycetous, Physomy- 

 cetous and Coniomycetous Fungi, but some 

 of the more common ones are especially 

 distinguished. Thus ordinary 'blue mould' 

 of cheese, &c. is ASPERGILLUS glaucus -, 

 another still more common blue or green 

 mould is PENICILLIUM glaucum ; various 

 species of OIDIUM and ERYSIPHE are known 

 as the mildews of the Hop, Vine, Rose, &c. 

 The mildew of wheat is PUCCINI A gra- 

 minis. 



MOUNTING. See PRESERVATION. 

 MOUSE, HAIR OF (PI. 1. fig. 3; PL 22. 

 figs. 27, 28). See HAIR OF ANIMALS and 

 TEST-OBJECTS. 



MOUTH. The mucous membrane of the 



mouth, which becomes continuous with the 

 skin at the lips, is furnished with very nume- 

 rous conical or filamentous papillae resem- 

 bling those of the skin, sometimes simple, 

 at others branched, and a number of mucous 

 glands. 



Its epithelium is of the pavement kind, 

 consisting of several layers of delicate cells ; 

 these are roundish in the deeper, flattened 

 and polygonal in the superficial layers. 



Fig. 496. 



Epithelial cells of the mucous membrane of the human 

 mouth, a, large, b, smaller cells ; c, one with two nuclei. 



Magnified 350 diameters. 



The glands, distinguished according to 

 their situation, as the labial, the buccal, and 

 the palatine glands, are rounded, about 1-36 

 to 1-6" in size, and open by short excretory 

 ducts into the mouth. They consist of 

 glandular lobules enveloped in areolar tissue 

 with elastic fibres, the whole being sur- 

 rounded by a firmer portion or capsule, and 

 a branched duct. The lobules are composed 

 of a number of convoluted canals or lobular 

 ducts, with simple or compound caeca or 

 glandular vesicles, each consisting of a base- 

 ment membrane, and a single layer of angu- 

 lar epithelial cells. The latter separate very 

 readily, and then the caeca appear filled 

 with a granular mass. 



