B. Cortex:

It occupies the major portion and can be divided into three different zones:

i. Outer (upper, peripheral) zone:

It shows two to three layers of big, ellipsoidal, schizolysigenous oil glands embedded in radially elongated parenchymatous cells. Oil glands have long radial axis and an epithelium which is composed of two or three layers of flattened cells. Parenchymatous cells contain tannins and thus show dark coloration with ferric chloride solution (alcoholic). This staining is also observed with alcoholic osmic acid. Many of the parenchymatous cells show cluster crystals of calcium oxalate.

i. Middle zone:

Within the oil gland layer, a zone of thick-walled cells is seen. Within these cells, a ring of bicollateral vascular bundles is embedded. About 20–25 bundles are present in the ring. The ground tissue contains cluster crystals of calcium oxalate. The vascular bundles are enclosed in an incomplete ring of lignified pericyclic fibers. The xylem is composed of three to five lignified spiral vessels.

iii. Inner (lower) zone:

It is made up of loosely arranged parenchymatous cells (aerenchyma) composed of air spaces. Air spaces are separated by lamellae which are thin and one cell thick. This region supports the central columella.

Powder Character:

The powder of the clove buds is dark brown in colour and possesses a characteristic, spicy aroma and pungent, slightly, characteristic, aromatic taste. The powder shows the following characters microscopically:

a. Hypanthium:

The fragments of hypanthium and the epidermis occur abundantly. The epidermis is made up of small, polygonal, thick-walled cells. It shows circular, big, anomocytic stomata along with large, brown, ovoid oil glands. A few cluster crystals of calcium oxalate are also observed. The fragments of hypanthium show a thick cuticle.

b. Oil glands:

These are numerous in the hypanthium, ellipsoidal to ovoid, large, brown and schizolysigenous associated with other parenchymatous tissues.

c. Parenchyma: The yellowish-brown parenchyma of hypanthium is abundant. Oil glands are found as embedded in this area. Cells are thickened and sometimes are collenchymatous. It shows a few small cluster crystals of calcium oxalate.

d. Calcium oxalate crystals:

The cluster crystals of calcium oxalate (sphaeraphides) are found in the parenchymatous cells. These crystals are of various sizes, rarely found scattered and made up of many small components.

e. Fibers:

These are sclerenchymatous, found singly or in groups of two to three in each group. These are short, broad and bluntly pointed. These show lignified thick walls with faint striations and small pits. The lumen is sometimes filled with brownish matter. These fibers are generally associated with parenchymatous cells or with small groups of vessels (fibrovascular bundle).

f. Aerenchyma:

Fragments of aerenchyma (loosely packed parenchyma) of the hypanthium are occasionally observed. These are made up of chains of two or three thick- walled parenchymatous cells. These chains show small intercellular air spaces separated by lamellae.

g. Sclereids:

These are from stalk and appear as oval to sub-rectangular with thick, striated walls and simple or branched pits. Some brownish matter is found inside the lumen.

h. Pollen grains:

These are small and biconvex with rounded or triangular shape and smooth exine. The immature pollen grains are found inside the pollen sacs.

i. Starch grains:

Starch grains are not observed in the case of the powder of clove buds. If these are observed in the powder, these come from mother cloves.