INSILELLA. 



[ 364 ] INTERCELLULAR SUBSTANCE. 



Phys. art. Insects ', Kirby and Spence, Intro- 

 duction to Entomology ; Burmeister, Handb. 

 d. Entomolog. (tr. by Shuckard) ; Siebold, 

 Lehrb. d. Vergl. Anat. ; Straus-Durckheim, 

 Consid, general, s. I Anatomie Comp. d. 

 Anim. Articul. ; Westwood, Introduction to 

 the Classification of Insects (copious Bibl.) ; 

 id. Butterflies of Great Britain ; V. d. Hoe- 

 ven, Handb. d. Zoologie; Blanchard, New 

 French edition of Cuvier's Regne Animal; 

 Stephens, Manual of Brit. Beetles; Laporte 

 and Castlenau, Hist. nat. d. Insect es ; Spry 

 and Shuckard, Brit. Coleopt. Delineated; 

 Kirby, Monogr. Apum Anglice ; Curtis, Brit. 

 Entomol. ; Panzer, Deutschlands Insekt. ; 

 and the innumerable Memoirs in the Ann. 

 des Sc. nat., the Annals of Nat. Hist., and 

 the Iiinncean Transactions. 



INSILELLA, Ehr.— A genus of Diato- 

 maceae. 



Char. Frustules single, fusiform, with a 

 turgid ring (hoop?) interposed between the 

 valves, which are equal. (Represents a fusi- 

 form Biddulphia.) 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". 



Found on the coast of Africa. 



Bibl. Ehrenberg, Ber. d. Berl. Akad. 

 1845, p. 357; Kiitzing, Sp. Alg. p. 32. 



INTEGUMENT or TEGUMENT.— The 

 cutaneous covering of the bodies of animals. 



INTERCELLULAR Passages, Spaces, 

 &c. OF Plants. — Where the cells of vege- 

 table tissue are of any but six- or twelve-sided 

 forms, interspaces must exist between them. 

 These are especially evident in parenchyma 

 formed of rounded cells, where there exist of 

 course, angular, intercommunicating, inter- 

 Fig. 372. 



Vertical section of half a leaf of a Potamogeton, with 

 air-spaces /. 



Magnified 200 diameters. 



qqWwX&x passages. The stomates of Leaves 

 always communicate with such intercellular 



passages, larger in the lower part of the 

 parenchyma of leaves. Intercellular 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 Nymphfeacese, 

 Naiadacese (fig. 372), and Hydrocharidaceae, 

 &c., but also common in most Mouocoty- 

 ledonous plants, such as Juncaceae (PI. 38. 

 fig. 18), Ai'aceae, Grasses, &c. 



Intercellular spaces and canals likewise 

 serve as Receptacles for Secretions, 

 as in the case of the glands of the Aurantia- 

 cese (fig. 284) (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 Tissue). 



Bibl. General works on Structural Bo- 

 tanv. 



INTERCELLULAR SUBSTANCE, of 

 Plants. — When we make fine sections of 

 many kinds of cellular structure, as for instance 

 of the horny albumen of the seeds of Palms 

 {Areca, PL 38. fig. 21 ) or other plants, of the 

 collenchymatous tissue beneath the epider- 

 mis of the Chenopodiaceae, &c., of the sub- 

 stance of cartilaginous Algae, of many woods, 

 &c., we find an appearance of intervals be- 

 tween the lines bounding the component 

 cells, which intervals are filled up with appa- 

 rently homogeneous substance. Thus seen 

 and no further investigated, the interposed 

 matter was formerly described as intercellular 

 substance, a peculiar form of vegetable orga- 

 nization, and some went so far as to imagine 

 that cells originated free in this, and subse- 

 quently became glued together and fixed by 

 the solidification of the whole (Unger and 

 Endlicher). The application of dilute sul- 

 phuric acid to preparations of this kind, with 

 iodine, generally shows clearly that the sup- 

 posed intercellular substance consists of 

 secondary deposits really inside the cells 

 (PI. 38. fig. 22). Recent observations go to 

 prove that the supposed intercellular sub- 

 stance, a matter secreted or otherwise pro- 

 duced between the cells of a tissue, is of 

 very rare occurrence, even if existing at all. 

 Many authors have written on the subject 

 during the last few years, and it is still one 

 of the vexed questions of Vegetable Ana- 

 tomy, standing in this respect beside the epi- 

 dermal or rather the cuticular structures, 

 with which it is very closely allied. The 

 following is a brief outline of those opinions 



