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SPECIES

Scientific name: Exacum zygomorpha
English name:
Vietnamese name:
Other name:

DESCRIPTION

Small achlorophyllous pure white mycoheterotrophic herb 5-8 cm tall. Roots numerous, clustering on short underground plagiotropic rhizome, fleshy, finely longitudinally wrinkled, separated by narrowing restrictions into fusiform portions 0.5-1 cm long, 1-2 mm in diam. Stem erect, slender, glabrous, branched like a simple cyme into 3 floriferous branches at the middle or in its lower portion, terete to indistinctly quadrangular, 1-2 mm in diam., indistinctly ridged, slightly swollen below nodes. Leaves numerous, opposite, scale-like, triangular, obtuse to acute, (1-)1.5-3 x 1-1.5 mm, internodes (3-)5-15(-20) mm long. Flowers terminal, solitary, 4-merous, asymmetric (zygomorphic-like), pure white, anthers dull light yellow. Calyx campanulate, slightly bisymmetric (having biaxial symmetry), 1-1.2 cm across, consist of 4 paired opposite, decussate, fleshy, spreading scales with distinct midvein, fused at the base; two outer scales narrowly triangular, acute, 5-6 x 2.5-3 mm; inner scales smaller and broader, shortly attenuate, with membranous, finely irregularly incised margin. Corolla of 4 petals, 10-12 mm long, zygomorphic; petals erect, connivent and obliquely one side turned, narrowly oblong, entire, 2.5-3 mm wide with 3 nerves, blunt or round at apex, joined on 2 mm from the base, forming globular tube 2 mm in diam., embracing ovary. Androecium slightly zygomorphic, stamens inserted at throat of corolla tube below sinus between petals, 8 mm long, shorter than petals (on 1-2 mm), all one-side turned; filaments subterete, 3.5-4 mm long; anthers 4 mm long, slightly curved, introrse, dorsifixed, sagittate, 1 mm wide at the base, narrowing to the apex, incompletely 2-locular, dehiscing by apical pores or abortive, indehiscent. Ovary of 2 carpels, 1-locular, broadly ovoid to globular 1.5 mm in diam., attenuate at the apex into distinctly bent, terete, thread-like style 8-8.5 mm long; stigma terminal, small, entire, truncate, discoid. Placentation free central with massive 4-lobed column bearing many ovules, divided to the apex into 4 short narrow sterile stalks. Fruits not seen. Etymology:—Species name refers to distinct zygomorph-like asymmetry of its flowers.

Distribution: Vietnam (Nghe An). Only one locality in Phu Xai Lai Leng Mountain on the border of the provinces Xiangkhouang (Laos) and Nghe An (Vietnam).

Ecology: Primary humid shady broad-leaved and mixed forests (with Cunninghamia konishii) on soils rich in humus derived from sandstone and shaly rocks at elev. 2000-2300 m, usually along ridge edges. It flowers from October-November. Very rare.


PHOTOS

Exacum zygomorpha 2.jpg at www.BotanyVN.com

Photo 1. Exacum zygomorpha 2.jpg

 

Exacum zygomorpha 3.jpg at www.BotanyVN.com

Photo 2. Exacum zygomorpha 3.jpg

 

Exacum zygomorpha 4.jpg at www.BotanyVN.com

Photo 3. Exacum zygomorpha 4.jpg

 

Exacum zygomorpha 5.jpg at www.BotanyVN.com

Photo 4. Exacum zygomorpha 5.jpg

 

Exacum zygomorpha 6.jpg at www.BotanyVN.com

Photo 5. Exacum zygomorpha 6.jpg

 

Exacum zygomorpha 7.jpg at www.BotanyVN.com

Photo 6. Exacum zygomorpha 7.jpg

 

Exacum zygomorpha Aver..jpg at www.BotanyVN.com

Photo 7. Exacum zygomorpha Aver..jpg

 

SCIENTIFIC CLASSIFICATION
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Gentianales
Familia: Gentianaceae
Genus: Exacum

PARAMETERS

BVN - BotanyVN - Botany Research and Development Group of Vietnam
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