INSILELLA. 



[ 438 ] 



INTESTINES. 



Arch. Phys. 1876, trachece ; Adolpli, Inseht- 

 Flilgd, If^SO ; Spauldiug, Amer. Nat. 1881, 

 XV. 113 {Jn. M. Soc. 1881, 442) ; Dritl, 

 Zeitschr. wiss. Zool. 1876, xxvii., brain; 

 M'Lachlan, JEnc. Brit. 1882, xiii. 141. 



INSILEL'LA, Ehr.— A genus of Diato- 

 macese. 



C/iar. Frustiiles single, fusiform, with a 

 turgid ring (hoop ?) interposed between the 

 valves, which are equal ; = a terete Biddul- 

 phia. Marine. 



I. africana. Frustules with four constric- 

 tions, broader and subglobose in the middle, 

 diminishing in size towards the acuminate 

 ends ; no markings visible by ordinary illu- 

 mination ; length 1-530 ; on the coast of 

 Africa. 



BiBL. Ehr. Ber. Berl. Ah. 1845, 357; 

 Kiitz. Sp. Ah/. 32. 



INTERCELLULAR Passages, Spaces, 

 &c. OF PX/ANTS. — Where the cells of vege- 

 table tissue are of any but six- or twehe- 

 sided forms, interspaces must exist between 

 them. These are especially evident in pa- 

 renchyma formed of rounded cells, where 



Fig. 368. 



Vertical section of half a leaf of a Potamogeton, with 

 air-8paces I. 



Magnified 200 diameters. 



there exist of course, angular intercom- 

 municating intercellular passat/es. The 

 stomata of Lea'vtis always communicate 

 with such intercellular passages, larger in 

 the lower part of the parenchyma of leaves. 

 Intei'cellular spaces are lacunae of larger 

 size, definite or indefinite in form, bounded 

 by a number of cells of less capacity than 

 the space itself. These are especially large 

 and abundant, as air-receptacles, in aquatic 

 plants, both in the stems and leaves, as in 

 the Nymphtcaceae, Naiadacese (fig. 368), 

 and Hydrocharidacea;, Sec, but also com- 

 mon in most Monocotyledonous plants, such 

 as JuncacejB (PI. 47. fig. 18), Araceae, 

 Grasses, &c. 



Intercellular spaces and canals likewise 



serve as Receptacles for Secretions, as 

 in the case of the glands of the Aui-antia- 

 cea3 (fi^. 280) (see also Glands), and the 

 turpentine-canals of the Coniferae. The 

 milk-vessels of plants appear to be formed 

 sometimes in intercellular canals, sometimes 

 out of cells (Laticiferous Tlssue). 



BiBL. "Works on Structural Botany. 



INTERCELLULAR SUBSTANCE of 

 Plaxts, or Secondary Cell-deposits. 

 — When we make fine sections of many 

 kinds of cellular structure, as for instance 

 of the horny albumen of the seeds of Palms 

 (Arecn, PI. 47. fig. 21) or other plants, of 

 the coUenchymatous tissue beneath the epi- 

 dermis of the Chenopodiacese &c., of the 

 substnnce of cartilaginous Algae, of many 

 woods, &c., we find an appearance of inter- 

 vals between the lines bounding the com- 

 ponent cells, which intervals are filled up 

 with apparently homogeneous substance. 

 Thus seen and no further investigated, the 

 interposed matter was formerly described 

 as intercellular substance, a peculiar form of 

 vegetable organization ; and some went so 

 far as to imagine that cells originated free 

 in this, and subsequently became glued to- 

 gether and fixed by the sohdification of the 

 whole (linger aud"Eodlicher). The appli- 

 cation of dilute sulphuric acid to prepara- 

 tions of this kind, with iodine, generally 

 shows clearly that the supposed intercellu- 

 lar substance consists of secondary deposits 

 really inside the cells (PI. 47. fig. 22). Re- 

 cent observations go to prove that the 

 supposed intercellular substance, a matter 

 secreted or otherwise produced between the 

 cells' of a tissue, is of very rare occurrence, 

 even if existing at all. Probably the 

 appearance is produced by modification of 

 the cell-wall. See Epiderjiis, Secon- 

 dary deposits. Wood, and Albumen. 



BiBL. Mohl, the BiBL. of Cell-mem- 

 brane ; Unger, An. u. Phys. Pfl. 1846, 18 ; 

 Mulder and Harting, Phys. Chem. ; Hartig, 

 Ann. Sc. Nat. 2 ser. v. ; Wigand, Intercdl. 

 Sub.it. 18-50; Cohu, Linna-a, xxiii. 337, 

 18-jO ; Schacht, Pflanzenzelle, Berlin, 1852, 

 76 ; Bentley, Bot. ; Henfrey-Masters, Elem. 

 Course. 



INTESTINES.— The intestines consist 

 of three coats : an outer, peritoneal, or 

 serous membrane, an inner or mucous mem- 

 brane, and an intermediate muscidar coat. 



The connective tissue of the mucous 

 membrane is often indistinctly fibrous, 

 especially its inner portions, where it forms 

 the basement membrane ; it contains scat- 



