Monocotylidonous Family: Orchidaceae

Systematic position

According to Bentham and Hooker it belongs to the series Microspermae. Engler places it under the order Microspermae.Hutchinson considers it as belonging to the order Orchidales of the divison Corolliferae.

Distribution

The family is large and is consisting of over 400 genera and more than 10,ooo species distributed in the tropical regions.

General  characters

Habit

Perrenial herbs of divers habits -terrestrial, epiphytes or mycorrizal saprophytes or xerophytes, epiphytes usually with swollen leaf bearing stem(pseudobulb) and with hanging aerial roots covered with velamen.

Leaves

Simple, alternate frequently distichous, often fleshy, linear or orbicular or ovate or strapshaped with sheathing leaf bases.

Inflorescence

Racemose, most frequently a spike or panicles or flowers solitary.

Perianth

Segments or tepals typically 6 to 2 whorls the outer usually sepaline and those in the inner whorl petaloid, the median segment of the inner whorl usually the largest and extreamely modified to form the leap or lebellum, usually projected into a basal sac, or spur, sometimes containing honey within.

Androecium

Stamens usually 1 and terminal, anther 2 celled, introse with 2-8 pollinia per anther or with granular pollens, the lower sterile portion of the pollinium sometimes prolonged into sterile filamentous cordlike structure, the caudicle, 1-2, staminodes frequently present.

Gynaecium

Carpels 3, united ovary inferior, usually 1-locular with many ovules on 3-double parietal placentae due to resupination of the ovary through two right angles, the labellum comes to the interior side of the flower, style 1, stigmas 3-lobbed, 2-laterals of which usullay fertile and often united with the third terminal lobe modified into a sterile outgrowth, the rostellum forming an integral part of the pollinium, the stigma, style and stamen(s) variously adherent together, a complex body, the column or gynandrium with the fertile stamen terminal on it.

Fruit

Capsules, dehiscing by 3-6 apically connete valves.

Seeds

Numerous very minute, non-endospermic embryo, indifferentiated.

 


Identifying Characters

  • Plant epiphytic or terrestrial herbs.
  • Flower zygomorphic, bisexual and epigynous showy.
  • Inflorescence racemose.
  • Perianth of two trimerous petaloid whorls, posterior petal larger.
  • Stamens 1, connet with the style in a column, pollen grain waxy.
  • Carpels 3, uniloculer with 3 parietal placentae.

Important Plants of Orchidaceae Family

Economically it is a very important family. Plants described here in different banners are:

Purpose   Plant name and comments
Image
Eadible

Platenthera sussanae

tubers are eadible

 

http://www.orchidspecies.com/orphotdir/pecsusanae.jpg
Image source:Here
Medicinal

Orchis latifolia

A nervine tonioc

 

Dactylorhiza incarnata - Kahkjaspunane sõrmkäpp Keila.jpg
Image source:Here
Flavouring Industry

Vanilla plannifolia

source of vanilla extract of commerce for flavouring various products

Image source:Here
Ornamental Cyperipedium sp.  

http://ereimer.net/20070323/10416_erCB720.jpg
Image source:Here
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About Mst. Nusrat Jahan Nitu

Mst. Nusrat Jahan Nitu
A 1st-year student of Department of Botany at the University of Dhaka. Opportunity seeker. Hope to do something remarkable.

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