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Phytolacca americana L. Phytolaccaceae A pale brownish-buff powder with a faint odour and a slightly bitter and acrid taste.

The diagnostic characters are:

(a) The starch granules, which are fairly abundant; they are mostly simple, spherical to ovoid with a rather indistinct, point or radiate hilum. The granules are frequently found clumped together in groups and a few compound granules also occur with up to four or more components.

(b) The very abundant fibres, which occur in groups and are frequently found associated with the vessels and xylem parenchyma; they are fairly thick-walled with few, simple pits and show no reaction for lignin.

(c) The idioblasts containing bundles of acicular crystals of calcium oxalate', the crystals vary in size and are frequently arranged somewhat irregularly in groups which are not always parallel to the long axis of the cell; they usually fill the cell completely. Single crystals or small groups of crystals are also found scattered in the powder.

(d) The abundant parenchyma containing scattered starch granules and, occasionally, bundles of acicular crystals of calcium oxalate; the cells are mainly thin-walled although occasional frag-ments show slight thickening; very occasional cells contain a brownish amorphous resin. Groups of xylem parenchymatous cells are also fairly abundant; the cells are elongated rectangular in outline with moderately thickened walls and numerous pits; they give a faint reaction for lignin.

(e) The vessels, some of which are large and may be found fragmented; they occur singly or in small groups and are frequently found associated with the groups of fibres and the xylem parenchyma. The walls are reticulately thickened or have elongated slit-shaped pits with large oval borders; they do not give a reaction for lignin.

(f) The brown fragments of cork composed of thin-walled cells; those from the root are polygonal and fairly regular in surface view, whilst those from the stem base are frequently more elongated and irregular in outline.

P h y t o l a c c a

x330 1 Cork from the root in surface view. 7 Acicular crystals of calcium oxalate.

2 Starch granules. 8 Cork from the stem base in surface view.

3 Part of a group of fibres. 9 Xylem parenchymatous cells (x.p.) showing 4 Fragment of a vessel showing bordered pits and pits, and part of a group of fibres in longitudinal

reticulate thickening. section.

5 Reticulately thickened vessels and part of a 10 Parenchyma of the phelloderm in sectional

group of fibres. view.

6 Parenchyma with two idioblasts containing aci-cular crystals of calcium oxalate.

PIMENTO

Pimenta dioica (L.) Merr. Myrtaceae

Allspice, Jamaica Pepper

A dark reddish-brown powder with a strong aromatic odour and a warm, aromatic and spicy taste.

The diagnostic characters are:

(a) The fragments of the epicarp in surface view with underlying parenchyma containing conspicuous, large, spherical oil glands. The cells of the epicarp are polygonal with moderately thickened walls and occasional large, rounded to ovoid stomata are present; fragments in sectional view show a thick cuticle. The oil glands have a distinct epithelium composed of a layer of thin-walled cells containing dense, reddish-brown pigment.

(b) The sclereids of the mesocarp, which are abundant and very characteristic; they occur singly or, more usually, in groups and they vary considerably in size, some being very large; the shape and the thickness of the walls is also very variable. In the majority the walls are distinctly striated and show numerous pits, and in the thicker-walled sclereids the pits are frequently branched.

Most of the cells contain brown pigment and they may sometimes be found associated with thin-walled parenchyma containing similar pigment.

(c) The thin-walled parenchyma of the mesocarp and dissepiment containing prisms and cluster crystals of calcium oxalate, which also occur scattered; the prisms are usually rather irregular in shape. Lignified fibres and vessels are frequently found associated with the parenchyma; the fibres usually have moderately thickened and pitted walls but occasional larger fibres occur in which the walls are heavily thickened; the vessels are small with annularly thickened or pitted walls.

(d) The abundant starch granules, a few simple but mostly compound with two or three components; individual granules are spherical to ovoid and are fairly small; they very occasion-ally show a stellate or slit-shaped hilum.

(e) The parenchyma of the cotyledons composed of polygonal to rounded cells with slightly thickened walls; in some of the layers the thickening is somewhat collenchymatous.

(f) The occasional layers of the testa in surface view. The epidermal cells are colourless, thin-walled and elongated; the cells of the underlying layers are larger and contain brown pigment.

(g) The very infrequent covering trichomes, which are found detached. They are unicellular, conical, with thickened walls and a smooth cuticle.

P i m e n t o

X330

1 Epicarp in surface view showing stomata and 9 Layers of a cotyledon in surface view.

parts of two underlying oil glands (o.g.). 10 Large sclereid in the mesocarp with associated 2 Sclereids from the mesocarp. parenchyma containing pigment.

3 Large, elongated sclereids from the mesocarp. 11 Starch granules.

4 Epidermis of the testa in surface view. 12 Covering trichomes.

5 Part of the mesocarp in longitudinal view show- 13 Prisms and cluster crystals of calcium oxalate, ing parenchymatous cells containing cluster 14 Outer region of the pericarp in sectional view crystals of calcium oxalate, thick and thin- showing the cuticle ( c ) , epicarp (ep.), paren-walled fibres and a pitted vessel. chyma and part of an oil gland (o.g.).

6 Thinner-walled sclereids from the mesocarp. 15 Part of the dissepiment in longitudinal view 7 Pigmented layer of the testa in surface view. showing a group of annularly thickened vessels 8 Fibres and parenchyma of the dissepiment with and adjacent pigmented parenchyma containing associated prism crystals of calcium oxalate. prisms and cluster crystals of calcium oxalate.

PODOPHYLLUM

Podophyllum peltatum L. Berberidaceae American Mandrake, American Podophyllum, May Apple Root, Podophyllum Rhizome A pale buff to sandy coloured powder with a bitter, slightly acrid taste and a characteristic odour reminiscent of Liquorice.

The diagnostic characters are:

(a) The abundant starch granules, most of which are compound with two to four or up to ten or more components; individual granules are rather small and the majority show a distinct circular or slit-shaped hilum.

(b) The vessels, which are usually fairly large and are frequently found fragmented; the walls are lignified and have elongated slit-shaped pits with oval borders or, occasionally, are scalariformly or reticulately thickened. A few smaller vessels also occur with spiral or annular thickening.

(c) The abundant parenchyma, filled with starch granules or, very occasionally, containing cluster crystals or calcium oxalate. The cells are rounded in outline and the majority are thin-walled but occasional groups of thicker-thin-walled cells are found and these show conspicuous pitting.

(d) The large cluster crystals of calcium oxalate; which are not very abundant; they are found scattered and, occasionally, in parenchymatous cells; they are frequently broken.

(e) The fragments of the epidermis of the rhizome composed of cells with reddish-brown contents; in surface view the cells are elongated with thin, sinuous walls. Underlying the epidermis there are two or three layers of large, thin-walled cork cells.

(f) The sclereids, which are not very abundant; they occur in groups composed of elongated rectangular cells with moderately thickened walls and numerous, conspicuous pits.

(g) The occasional brown fragments of the outer layer of the rootlets composed of cells which, in surface view, are elongated and irregular in outline and have moderately thickened walls;

fragments in sectional view show that the thickening occurs on the outer and side walls only.

Compare Indian Podophyllum, page 128.

P o d o p h y l l u m

X330

1 Fragments of bordered pitted vessels. 6 Pitted parenchyma.

2 Fragments of reticulately thickened vessels. 7 Outer layers of the rootlets in sectional view.

3 Starch granules. 8 Part of a group of sclereids.

4 Epidermis of the rhizome in surface view. 9 Outer layers of the rootlets in surface view.

5 Epidermis and underlying cork cells in sectional 10 Cluster crystals of calcium oxalate and a group

view. of parenchymatous cells.