STIPA. 



[ 741 ] 



STOMATA. 



exliibit the Rotatiox. Stings occur not 

 only ill the nettles (Urfica), but in the 

 cultivated Loasacene {Loa/^a, Bartonia, Sec), 

 and of much larpn- size in some exotic 

 Urticacete and Euphorbiacese. 



See Hairs, page 378. 



STI'PA, Linn. — A genus of Graminacefe. 

 The fibres of the culms of -S'. tenacissima 

 are used in the manufacture of paper. 



STOMACH.— The glauds which secrete 

 the gastric juice, or the peptic glands, are 

 tubular, and placed perpendicularly beneath 

 the surface uf the mucous membrane, and 

 extending as deeply as the muscular coat of 

 the stomach. 



They vary in length from 1-60 to 1-12", 

 are cylindrical, somewhat narrowed towards 

 the closed end, which is rounded or some- 

 what inflated. The lower third is wavy or 

 spiral, especially in the glands occupying the 

 pylorus ; some of them also give on a ctecal 

 Dranch. 



The peptic glands consist of a delicate 

 basement membrane, lined in the upper 

 third with cylindrical epithelium, the lower 

 portion being tilled with large, pale, poly- 

 Fig. 705. 



Perpendicular section of the pyloric portion of the 

 stomach of a pig. a, glands ; b, muscular layer of the 

 proper mucous membrane; c, submucous tissue with 

 the oritices of divided ressels ; d, transverse muscular 

 layer; e, longitudinal ditto; f, serous coat. Magnified 

 30 diameters. 



gonal, finely granular cells, not arranged in 

 a laminated form. 



In many animals the gastiic glands are of 

 more complicated structure than in man, and 



two distinct l<inds exist — in one, secreting 

 mucus, tlie tubes being lined with cylin- 

 drical epithelium; wliilstin tlie other, wiiich 

 secretes gastric juice, rounded epitlidi <\ 

 cells occur, and the walls tu'e expanded at 

 intervals. 



Closed follicles resembling the solitary 

 glands of the small intestines are met with 

 in the stomach ; they are inconstant, how- 

 ever, and variable in number. 



The stomach is lined by cylindrical epi- 

 thelium. 



BiBL. KoUiker, Mik. An. ii. 1.37, and the 

 Bibl. therein ; Todd and Bowman, Phi/s. An. 

 ^•c. ; Briuton, TodxVs Cycl. An. ^- Phys. Art. 

 Stomach ; Klein, Strieker'' s Hist. i. 1543. 



STOM'ATA (plural of Stoma).— The 

 name applied to the structures which con- 

 stitute the passages of communication, 

 through the Epidermis of plants, from the 

 intercellular passages to the external air. 

 They occur almost exclusively on the green 

 parts of plants, and are usually absent from 

 the epidermis of roots, and the siu'face of 

 all structures growing under water. The 

 lowest classes which present them are the 

 Liverworts and Mosses, where, however, 

 they are limited to a few kinds, and in the 

 former present a pecidiar organization. In 

 the Ferns they are distributed just as in 

 the Flowering Plants, where they occur 

 principally upon the leaves (fig. 706), 

 especially upon the lower face, but ex- 

 tend also over the green shoots, the parts 

 of the flower (fig. 200, page 296), and even 

 into the interior of cavities, as on the epi- 

 dermis of the replum of Cruciferre (wall- 

 flower), and still more remarkably on the 

 epidermis of seeds (skin of the walnut). 



In the Liverworts the stomata occur on 

 the fronds and receptacles of certain genera 

 {Marehanlia, Feyatella, &c. &c.). In Mar- 

 chantia (fig. 447, p. 489), they are somewhat 

 circular orifices in the epidermis, guarded 

 by cells arranged in three or fom* tiers. In 

 the Mosses they are met with on the apo- 

 physes or thickened summits of the setas 

 bearing the capsules, as in Funaria (fig. 262, 

 page 343). The structures here resemble 

 those in the higher pkint.j, as is the case 

 also with those on the leaves of Ferns. 



In the Flowering Plants the perfect sto- 

 mata appear as roundish or sometimes 

 squarish chasms in the epidermal layer, 

 occurring regularly at the meeting angles 

 or sides of four or more epidermal cells, the 

 chasm forming an orifice leading down to a 

 subepidermal intercellular space, and guar- 



