Grass Identification
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Classification of Grasses - continued

Classification of Grasses

(The numbers of genera given are for Britain only)

 The Flowering Plants are divided into two groups, the Monocotyledons and the Dicotyledons.

Grasses, sedges and rushes all belong to the Subclass Monocotyledons. They can easily be distinguished from the Dicotyledons in that they have:

  • 1 seed leaf.
  • Leaves with parallel veins.
  • Fibrous roots.
  • Scattered vascular bundles (conducting tissue within the stems).

The grasses and the sedges belong to the Order Graminales (a further subdivision of the Monocotyledons).

 

Features of the Order Graminales

  • The flowers are inconspicuous, are arranged in spikelets and enclosed in chaffey (papery) scales. They do not have petals and sepals (image of a grass flowering head here).
  • The fruit is one seeded. Its seed coat is united with the ovary wall and is called a Caryopsis.

Grasses are in the Family Poaceae, (also known as Gramineae), and Sedges are in the Family Cyperaceae.

The main differences are:

Grasses  

Sedges

Cylindrical, usually hollow stems.

Triangular, solid stems.
wpe149.jpg (5196 bytes) Alternate leaves, in 2 ranks.
Sedge - leaves in threes Leaves in 3 ranks.

Flowers have 3 types of bracts.

Flowers have a single type of bract.

The Rushes are in the order Liliales and have many similar features to Lily flowers, except that the petals and sepals are small, brown and scale-like and are called tepals. (They are called tepals collectively, because the sepals and petals look exactly the same and are indistinguishable from each other.) Rushes belong to the Family Juncaceae. The main features of this family are:

4 individual flowers of Woodrush. The brownsih outer scales are the tepals.
  • Each flower is composed of 2 rings of tepals.
  • Inside the perianth (the rings of tepals) are one or two rings of 3 stamens.
  • In the centre is the ovary with 3 stigmas.
  • The fruit is a capsule.

         (General flower structure in flowering plants here)

There are 2 genera of rushes in Britain, (in contrast to the 54 genera of grasses).

Woodrush plant, including the inflorescence.

  

Luzula (Woodrushes) which have hairy, grass- like leaves and 3 seeded capsules (left).

 

 

Juncus (Rushes) which have hairless, cylindrical stem-like leaves and many seeded capsules (right).

 

Soft Rush, with a closer view of the inflorescence (inset).

Continue to

Grass Structure

 

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