MOULDS. 



[ 438 ] 



MOUTH. 



formed iii 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 w^hich 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- 

 jiexa, 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- 

 nujiexa, 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 notahilis, Hass. {Sirogonium 

 notabile, Kiitz.) is an obscure plant, perhaps 

 referable to this genus. 



BiBL. Vaucher, Conferves 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 ^ZaMCwm ; various 

 species of Oidium and Erysiphe are known 

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

 The mildew of wheat is Puccinia gra- 

 minis. 



MOUNTING. See Preservation. 

 MOUSE, hair of (PI. 1. fig. 3; PI. 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 cffica 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. 



