MIMOSACEAE (Mimosa or Acacia family)

MIMOSACEAE (Mimosa or Acacia family)

This family has 56 genera and about 2800 species. There are 11 genera and 49 species in Pakistan. Only 4 genera or 18 species are native. The remaining species are introduced.

Familiar Plants

➤ Acacia nilotica

➤ Albizzia lebbek 

➤ Mimosa pudica, Touch me not

➤ Prosopis glandulosa

➤ Prosopis cineraria

Vegetative Characters

1. Habit: Mostly trees or shrubs. Rarely climbers or herbs. Most of them are xerophytes.

2. Stem: Mostly woody

3. Leaves: They have pinnate, compound, alternate and stipulate 1eaves. The stipules are modified into thrones.

Floral Characters 5 + 5 + 5 + 1

1. Inflorescence: It is spike like or head or umbel. It is rarely racemose or Globose umbel.

2. Flowers: The flower is bisexual, actinomorphic, hypogynous to slightly perigynous and bracteate.

3. Calyx: They have 5 sepals. These sepals are fused, toothed or lobed.

4. Corolla: They have 5 petals. These petals may be free or fused.

5. Androecium: Stamens are five to numerous. They are free, adnate or attached to base of corolla (epipetalous).

6. Gynoecium: They have simple one carpel. Ovary is unilocular and superior. It has many ovules. Placentation is marginal.

7. Fruit: Fruit is a legume. The legume may be dehiscent or Indehiscent.

POACEAE (Gramineae) Grass Family

This family is distributed throughout the world. It has 600 genera and 10,000 species. There are 158 genera and 492 species of this family in Pakistan.

Familiar Plants

➤ Triticum vulgare, wheat

➤ Zea mays, corn

➤ Avena sativa, oat

➤ Oryza sativa, rice

➤ Bambusa, bamboo 

➤ Saccharam officinarum, Sugar cane.

Vegetative characters

1. Habit: Annual or perennial herbs.

2. Stem: The stem is jointed and usually hollow at the internodes. It is closed at nodes.

3. Leaves: Leaves are solitary at node. They are sometimes, crowded at the base of the stem. These leaves are simple, alternate, exstipulate and mostly sessile. The leaf bases are mostly sheathing.

Inflorescence

The grasses have compound inflorescence. Tnit of this compound inflorescence is called spikelet. The spikelets are variously arranged.

(a) They may form dense clusters as in wheat compound spike.

(b) They may be arranged on a branched axis-panicle as in spikelets of oat.

The spikelets are composed of following structures:

1. Rachilla: The spikelets are arranged on a slender axis called rachilla.

2. Bracts: Each spikelet consists of florets. The spikelets and florets at covered with following bracts.

➤ Glumes: The lower two empty bracts are called glumes. The glumes cover whole of the spikelet.

➤ Lemma and palae: The upper bract is called lemma. It encloses the flower. A hyaline scale like bract is present opposite to lemma. It is called palea. Lemma and palae cover the floret.

3. Floret: The whole structure consisting of lemma, palea and flower is called floret.

4. Awns: The glumes or lemmas also contain one or more bristle like structures called awns.

This basic pattern of spikelet is present in all the members of this family. The spikelets of grasses vary in different genera. They have different number of fertile florets and different number of sex organs in them.

Flower

Flower is usually bisexual (sometimes unisexual), small, inconspicuous, sessile, bracteate, incomplete, zygomorphic and hypogynous.

1. Perianth: It is absent or it is represented by 2 (rarely 3) scales called lodicules. These lodicules are hyaline or fleshy.

2. Androecium: They have 1 to 6, mostly 3, free stamens. The stamens have delicate filaments. Their anther is versatile.

3. Gynoecium: They have a compound pistol with three united carpels. Only one carpel is functional. Stigma usually large and feather like.

Fruit

There fruits are grains or caryopsis. Caryopsis is a dry indehiscent fruit in which fruit wall (pericarp) is completely fused with the seed coat.