OSMUNDA. 



[ 478 ] 



OVARY. 



XXI. AINACTIS. Filaments branched, 

 articulated, with thin sheaths, collected into 

 a solid, pulvinate frond, which is concen- 

 trically zoned by the dichotomous branching 

 of the filaments. Sheaths more or less soli- 

 dified by carbonate of lime ; sometimes ex- 

 hibiting a spiral structure in dissolution. 



XXII. RIVULARIA. Filaments with an 

 oval basal cell succeeded by one of cylindric- 

 al form (manubrium), the remainder short, 

 attenuated in diameter upwards (whip- 

 shaped). Sheaths sometimes saccate below, 

 open (not fringed) above ; forming a slippery 

 gelatinous frond. 



XXIII. EUACTIS. Filaments whip- 

 shaped, with repeated ochreate sheaths, 

 forming fronds in which they radiate, and, 

 by superposition of successive generations, 

 form concentric layers. The ochreate sheaths 

 are cartilaginous, lamellated, firmly united 

 laterally, dilated upwards (funnel-shaped), 

 decomposed into a fringe at the open edge. 



XXIV. INOMERIA. Filaments whip- 

 shaped, vertical, parallel, with obscure 

 sheaths, everywhere decomposed into very 

 slender filaments; forming crustaceous fronds, 

 becoming stony. 



E. Leptothricece. Doubtful Oscillatoriacese. 



XXV. LEPTOTHRIX. Filaments very 

 slender, neither branched, articulated, con- 

 creted, nor sheathed. 



XXVI. HYPHEOTHRIX. Filaments un- 

 branched, inarticulate, sheathed, interwoven 

 into a more or less compact stratum. 



XXVII. SYMPLOCA. Filaments un- 

 branched, inarticulate, sheathed, concreted 

 into branches, conjoined at their bases; 

 sheath a simple hyaline membrane. 



Excluded Genera. 



Stigonema, Ag. See EPHEBE. Arthro- 

 siphon,Ktz.=Petalonema. Chthonoblastus, 

 Ktz. = Microcoleus. Hassallia, Berk. = 

 Sirosiphon. Lithonema } l^.Si&s.=Amactis. 

 Phormidium, Ktz . = Oscillatoria. Sympky- 

 othrix, Ktz. = Oscillatoria. Spirochceta, 

 Ehr. = Spirulina. Spirillum, ~Ehr.=Spiru- 

 lina, and also SPERMATOZOIDS of Mosses 

 and Characeae. Spirodiscus, Ehr. ? 



BIBL. See the genera, especially OSCIL- 

 LATORIA and RIVULARIA, and SPIRAL 



STRUCTURES. 



OSMUNDA, Linn. A genus of Osmun- 

 deaeous Ferns, represented in Britain by 

 Osmunda regalis (figs. 226, 227, p. 260), the 

 ' Royal or Flowering Fern,' as it is termed, 



a large and handsome plant, found in damp 

 situations ; riot common. 



OSMUNDE^E. A tribe of Polypodea- 

 ceous Ferns, characterized by the broad im- 

 perfect annulus on the back of the sporanges. 



Synopsis of Genera. 



I. OSMUNDA. Sporangia borne on meta- 

 morphosed pinnules. 



II. TODEA. Sporangia placed on un- 

 changed pinnules. 



OTOGLENA, Ehr. A genus of Rotato- 

 ria, of the family Hydatinsea. 



Char. Eyes three ; one sessile and cervi- 

 cal, the two others stalked and frontal. 



Neither jaws nor teeth present. 



O. papillosa. Body campanulate, turgid, 

 rough with papillae ; aquatic ; length 1-96". 



BIBL. Ehrenberg. Infus. p. 453. 



OVA, OF ANIMALS. The germs secreted 

 by the ovaries. When extruded from the 

 body, they are generally termed eggs(EGGs). 

 See OVUM. 



OVARY. The organ in which the ova or 

 germs of the future offspring are formed 

 and temporarily contained. 



The ovary consists of an outer fibrous 

 coat, and a parenchyma or stroma. 



The outer coat, or tunica albuginea, is 

 firm, white, and intimately connected with 

 the subjacent stroma; it consists of inter- 

 lacing bundles of areolar tissue, with but 

 few fibres of elastic tissue. 



The stroma (fig. 543 e) is composed of 

 nucleated areolar tissue, in which the fibrillae 

 are mostly indistinct, and in it are imbedded 

 the Graafian vesicles or follicles (fig. 543 a). 



Transverse section of a human ovary at the fifth month 

 of pregnancy, a, Graafian vesicle of the under, b, of the 

 upper surface ; c, peritoneal layer continued from the 

 broad ligament of the uterus to the ovary, and becoming 

 fused with d, the tunica albuginea ; in the centre are two 

 old corpora lutea ; e, stroma of the ovary. 



The vesicles vary greatly in number and 

 size ; the largest are generally nearest the 



