142 ORCHIDACEAE. 15. Diuris. 



15. DIURIS, Sm. 



(Greek dis, two ; oura, a tail : referring to the lateral sepals.) 

 Dorsal sepal erect or slightly recurved at the apex, more or less ovate, its tip biunt'and 

 its base clasping the column ; lateral sepals narrow-linear, often herbaceous, spreading or 

 deflexed, parallel or crossed, exceeding the dorsal sepal in length. Petals longer than the 

 dorsal sepal, oval, elliptical or orbicular on slender stalks, erect or spreading. Labellum 

 usually as long or longer than the dorsal sepal ; deeply 3-lobed (text fig. 33, A ; lib, ml.) ; 

 the middle lobe much contracted at the base, with 1 or 2 raised longitudinal lines along the 

 narrow part. Column very short, the sexual elements arising separately from the floral 

 receptacle (figs. 1-4) at first quite separate, but united as the flower approaches maturity, 

 by an adhesion between the pollen-masses and the viscid disk of the rostellum. Anther 

 erect, 2-celled, on a very short filament, margins of the filament produced into erect 

 lateral lobes or wings not adnate to the stigmatic -plate. Stigma borne on a widened 

 style or " plate " in front of the anther, a slot in its upper border representing the ros- 

 tellum and likewise enclosing the locse viscid disk, the latter attached at maturity to the 

 apices of the pollinia without intervention of a caudicle. Pollinia 2, each deeply bilobed, 

 suspended behind the stigma from the back of the viscid disk. Pollen -masses mealy. — 

 Terrestrial glabrous plants with underground tubers and several imbricated scales at 

 base of the scape. Leaves more than one, generally several, narrow, at or near the base, 

 with a few stem -bracts higher up. Flowers 1, 2, or more, in a terminal raceme, rather 

 large and conspicuous, yellow, purple or white, often spotted or blotched with dark -brown 

 or purple. 



The genus is endemic to Australia, and contains 26 valid species. 



Flowers not blotched or spotted on their upper surface, but 

 of a uniform color. 

 Flowers purple or heliotrope (drying yellowish-brown) ; 

 lateral sepals greatly exceeding petals, about 5 cm. 



long D. punctata 1. 



Flowers canary-yellow ; lateral sepals only slightly 



exceeding petals D. pedunculata 2. 



Flowers yellow with conspicuous dark-brown or purple- 

 brown markings or blotches. 

 Lateral lobes of labellum large, as long or nearly as long 

 as middle one. 

 Lateral sepals greatly exceeding petals in length, often 

 nearly twice as long ; leaves 6 or more, setaceous 



or almost so D. palustris 3. 



Lateral sepals shorter than, or approximating in length 

 to the petals ; leaves not setaceous. 

 Lateral sepals crossed ; blotches generally distinctly 

 demarcated from the yellow ground-color ; 2 

 longitudinal raised lines at base of labellum ... D. maculata 4. 

 Lateral sepals nearly parallel ; flowers wall-flower 

 color, dark blotches merging into yellow ground- 

 color ; 1 raised line at base of labellum D. longifolia 5. 



Lateral lobes of labellum very much shorter than the 

 middle one. 

 Two raised longitudinal lines along base of labellum. 

 Flowers with small dots and short linear markings ; 



leaves linear and rather lax, often 17 cm. long. . D. palachila 6. 

 Flowers with 2 conspicuous brown dots at base of 

 dorsal sepal and conspicuous oblong brown 

 border round the raised lines ; leaves usually 

 more than 5, setaceous or nearly so ; short 



(about 7 or 8 cm.) and very erect D. brevifolia 7. 



One longitudinal raised line along base of labellum. 

 Flowers with similar markings to D. brevifolia, and 

 in addition a brown transverse blotch near the 

 tip of middle lobe of labellum ; leaves usually 

 2, rarely 3, long lax, linear D. sulphurea 8. 



1. D. punctata (dotted, a misnomer), Sm. Slender, glabrous, 30-60 cm. high. Leaves 

 usually 2, linear, channelled, 15-20 cm. long. Flowers 2-5, heliotrope, not dotted, on 

 long slender pedicels enclosed more or less in loose subulate bracts. Dorsal sepal broadly 

 ovate, erect, or recurved at apex, about 16 mm. long ; lateral sepals about 5 cm. long, 

 green, very narrow -linear, spreading, usually parallel. Petals on a narrow claw, about 

 6 mm. long ; lamina elliptical or elliptical- oblong ; total length about 22 mm. Labellum 

 purple, about 14 mm. long ; 3-lobed ; middle lobe broadly ovate or semicircular on 

 a narrow base; lateral lobes less than half as long, oblong-falcate, erect with outwardly 

 curved tips, margins entire or crenulate ; lamina traversed at the base by 2 conspicuous 



