EPITHELIUM. 



[ 299 ] 



EQUISETACEyE. 



In most opithelia, the cells and tlioir 

 nuclei are readily distinguished ; but in 

 others, especially those of the vessels and 

 serous membranes, staining with magenta, 

 kc, is required to render the nuclei dis- 

 tinct, and silvering to bring out the cell- 

 boundaries, (See Staining.) 



In many cases, intervals are left between 

 the epithelial ci'lls, usually at the points 

 where several cells meet ; these are called 

 stomata. They are often connected with 

 the lymphatic system. See Stomata. 



The epithelium covering the outer svu- 

 face of the body forms the epidermis or 

 cuticle. 



Further particulars of the special forms 

 of the cells are given under the heads of 

 the organs or tissues in connexion with 

 which the epithelia are found. 



BiBL. KoUiker, Mikr. An. and Handb. 

 d. Geivebel. ; Valentin, Tfcu/iier's Handb. d. 

 Pliys., art. Flimmerbeiveyunf/ and Epitltel. ; 

 Henle, Allgemein. An. ; Todd and ] bow- 

 man, Phys. ; Frey, Histologie, 1876, 153 and 

 the full literature. 



EPITHELIUM OP Plants. See Epi- 

 dermis of Plants. 



EPITHE'MIA, Brebisson.— A genus of 

 Diatomacea3. 



Char. Frustules suigle, attached by a part 

 of the surface to other bodies ; valves with 

 transverse or slightly radiant strias, some of 

 them not resolvable into dots. 



Frustules prismatic, quadrangular, mostly 

 curved, sometimes slightly undulating in 

 the side view ; one face of front view (that 

 by which they are attached) flat or con- 

 cave, the other convex and broader than the 

 former, so that the transverse section forms 

 a trapezoid. Between, or corresponding 

 with the transverse striae, which are not 

 resolvable into dots, are often transverse 

 rows of dots or depressions. 



The species are numerous. Fi'eshwater 

 and marine. Rabenhorst describes 21 Eu- 

 ropean. Conjugation has been observed in 

 three of them. 



E. turyida (PL IG. fig. 32 : a, side view ; 

 h, front view). Front view oblong, slightly 

 dilated towards the middle ; side view some- 

 what convex, g-radually attenuated towards 

 the very obtuse ends. Freshwater ; length 

 1-240".' In conjugation, PL 10. fig. 6 a, b, 

 c, d, e. 



E. gibba (PI. 51. fig. 6). Straight ; in- 

 flated in the middle on each side in front 

 view ; A^alves gibbous in the middle on one 

 side J freshwater and fossil; length 1-140". 



BiBL. Kiitzing, BnciUar. 33, and Sp. 

 Aly. 1 ; Smith, Brit. Diatom, 1. 13 ; Ra- 

 benhorst, Sp. Al(). i. 02. 



EPOCIPNIUM, Lk.— A genus of Toru- 

 lacei (Hyphomycetous Fungi), forming a 

 stratum over larger fungi or dead twigs, 

 consisting of a mycelium of irregularly 

 branched and anastomosing filaments, which 

 bear, on short lateral branchlets, oblong or 

 globular septate spores, which soon faD off 

 and lie among the mycelium-threads, 



E. fungorum is very common, forming' a 

 dark-green stratum over Thdephorce; E.ma- 

 crosporoidium was found by 13erkeley on a 

 dead twig, apparently of red currant. 



SphcBria Epochnii, B. & Br., has been 

 found on Epochnium fungorum:, and it is 

 very probable that it is the perfect state of 

 a conidiiferous mycelium. 



BiBL. Berk, in Brit. Flora, vol. ii. pt. ii. 

 3o2 ; An7i. N. H. i. 263, pi. 8. fig. U. 



EQUISETA'CE^E and EQUISE'TUM. 

 — This is a very distinctly characterized 

 family of Flowerless Plants, consisting of a 

 single genus, the Equiseta, or Horse-tails, 

 which are immediately recognized, when 

 one species is known, by their peculiar aspect 

 andhabit of growth. The stems and branches 

 are alike tubular, and present in almost all 

 cases a rather coarsely (per- 

 pendicularly) streaked sur- 

 face. The stems appearing 

 above ground are shoots 

 from a creeping under- 

 ground stem (fig. 201), 

 which differs from the 

 erect stems in being of 

 a deep brown colour and 

 solid, in giving off root- 

 fibrils, and sometimes in 

 being covered with hairs. 

 The erect stems are either 

 barren or fertile ; in the 

 barren stetns the joints be- 

 come gradually thinner 

 upwards from a certain 

 point, at last tapering off • 

 to an obtuse apex; the fer- 

 tile stems bear a kind of 

 club-shaped head, resem- 

 bling in some degree the Equisetum arvense, 

 male cones of Coniferous One half of 

 trees, or more particularly "'i'- ^'^e, 



those of some Cycads (fig. 201). These 

 club-shaped bodies are the fruits or heads 

 of sporauges. 



The anatomical structure of the rhizome 

 and shafts present some interesting points. 



201. 



