Grass Identification
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Grass Structure

TThe Grass Plant
The structure of grass plants

The roots are fibrous

Grass Stems -  are mostly hollow, cylindrical and interrupted at intervals by swollen joints or nodes.

Stems are rarely branched above the ground and are called CULMS.

Some grasses have stems which creep along the surface of the ground and give rise to new  shoots (TILLERS) at their nodes. The horizontal stems are called STOLONS.

If the horizontal stems go underground they
are called RHIZOMES. 

Leaves - originate from the nodes.  The lower portion of the leaf forms a sheath, which encloses and protects the young shoots. The second half of the leaf then opens out into the leaf blade.


Grass Leaf Structures

The leaf blade is usually long and narrow, with parallel sides and veins and tapering to a pointed or blunt tip. 

At the junction of the sheath and blade there is a small membranous flap of tissue called the LIGULE (image here). This is sometimes just a fringe of hairs (image here).

In some grasses there are also
projections on either side of the ligule called AURICLES.

The structure and dimensions of the sheath, blade and ligule, and their hairiness provide good diagnostic features for identification.

The part of the grass plant popularly known as the flower, is actually composed of many small flowers hidden, except at flowering time, within scales or bracts. The structures containing the flowers are called SPIKELETS.
The Grass Flower
Grass floret The flower is usually bisexual. It consists of an ovary containing 1 ovule (the female part). The ovary is usually surmounted by two feathery stigmas and is surrounded by three stamens. Each stamen (the male part of the flower) consists of an anther (image here) and a filament.

There are no petals or sepals. Instead, the flower is protected by two sets of scales.  The first set consists of the LEMMA and the PALEA which enclose the flower. This whole structure is called a floret.

(More on the flower structure of Flowering Plants here)

A spikelet containing six florets  

One or more florets may be arranged on an axis (the RACHILLA), with all of the florets being protected by a second set of scales at the base called GLUMES. The glumes enclose the florets before they are mature.

The whole unit is called a SPIKELET(image here). The Lemmas (of individual florets) and/or the Glumes, may have bristle-like extensions called AWNS arising from them.

(Left: a spikelet made up of 6 florets)


A spikelet with 2 florets

A spikelet made up of 2 florets

(image here)

The spikelets are arranged into a flowering head (inflorescence) in a number of different ways depending on species.


Arrangement of Spikelets into a Flower Head or Inflorescence



When the spikelets  are borne on stalks on branches from the main axis, the flower-head is called a PANICLE (image here).


(In this diagram of a Panicle, the spikelets are depicted as brown ovals)



If the spikelets are stalked directly on the main axis, then the flower-head is a RACEME.



Where there are no stalks, and the spikelets are seated on the main axis itself, the flower-head or ear is known as a SPIKE (image here).

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Ten top tips for identifying grasses