CHAPTER I ROOTS AND RHIZOMES (Part 1)

CHAPTER I ROOTS AND RHIZOMES Some fifty-five roots, rhizomes, and rhizomes and roots are official in the pharmacopoeia and national formulary. About 5 of these are obtained from monocotyledonous plants, and 50 from dicotyledonous plants. In studying the structure of roots and rhizomes, then, it must first be determined whether the root in question is mono- cotyledonous or dicotyledonous. This fact is ascertained by determining the type of the fibro-vascular bundle. The bundle is of the open collateral type in all rhizomes and roots obtained from monocotyledonous plants, but it is closed, radial, or con- centric in the monocotyledonous type. In both of these groups the cellular plan of structure is similar, the chief variation being the absence of one or more types of cells, the variation in the amount, in arrangement, in the anatomical structure, in the color, and in the cell contents of the individual cells. These facts will be impressed on the mind while studying the rhizomes and the roots. CROSS-SECTION PINK ROOT The cross-section of pink root (Plate 89) has the following structure: Epidermis. The epidermal cells are small, nearly as long as broad, and the outer wall is thicker and darker in' color than the side and inner walls. The cells usually contain air. Cortex. The cortical parenchyma cells are very large and somewhat rounded in outline, and the waUs are white. There are about twelve rows of these cells, and each cell contains nimierous small, rounded starch grains. Endodermis. The endodermal cells are tangentiaUy elon- gated, and the walls are very thin and white. There are two or three layers of endodermal cells; the cells' outer layers are larger than the cells of the inner layers. 219 Csoss-SBcnoN OF Root of Shcelia hakvlandica, L. p. E|Hdermia. 3. Cortical parenchyma. 2'. Intercellular space, dtxl^rmis. 4. Pericydc. 5, Cambium. 6. Xylem. 7. Pith. ROOTS AND RHIZOBCES 221 Pericycle. The cells forming the pericycle are sieve cells and phloem parenchyma. The sieve cells are small, angled cells with extremely thin, white walls. The phloem parenchyma resemble the sieve cells, except that they are larger. Cambium. The cambiiun cells are rectangular in shape; the walls are thin and white. Xylem. The xylem is composed of tracheids, wood paren- chyma, and wood fibres. Tracheids. The tracheids are the largest diameter cells of the centre of the root. The walls are thick and the cells are slightly angled in outline. Wood Parenchyma. The wood parenchyma cells surroimding the tracheids are five to seven, angled, and the walls are not so thick as the walls of the tracheids. Medullary Rays. The medullary ray cells resemble the structure of the wood parenchyma cells, but they are radially elongated. Pith Parenchyma. The cells forming the pith parenchyma are larger than the cells of wood parenchyma, but their struc- ture is similar. CROSS-SECTION RUELLIA ROOT The cross-section of ruellia root (Plate 90) shows the follow- ing structure. It should be carefully noted how the structure differs from that of pink root: Epidermis. The epidermal cells are angled and variable in size; many of the epidermal cells are modified as root hairs. Hypodermis. The cells of the hypodermis are one layer in thickness and their structure is similar to the epidermal cells. Cortex. The cortex contains parenchyma and stone cells. The outer layers of the cortical parenchyma cells are roxmd in outline, and they contain dark-brown cell contents, while the cortical parenchyma cells bordering on the endodermis are small and they are free of dark-brown contents. Many of the inner parenchyma cells contain amorphous deposits of calcium carbonate. RimLUA Root {Rudlia eUiosa, Pursh.). I. Epidermis with root hair. i. Parenchyma cells with dark contri 3. Sclend. 4. Parenchyma without dark cell cnntents. 5. EndodiTr 6. Bast fibers and phloem. 7, Cambium. 8. Xyli.'m. 10. Pith. ROOTS AND RHIZOMES 223 The stone cells are porous and striated, and the walls are thick and white. Endodermis. The endodermal cells are tangentially elon- gated, and the walls are thin and white. Pericycle. The cells forming the pericycle are the sieve cells, bast fibres, and phloem parenchyma. The sieve cells are small, angled cells with thin, white walls. The phloem parenchyma cells resemble the sieve cells, but they are larger. The bast fibres occur singly or in groups of two or three. They are rounded in outline, and the walls are white, non- porous, and non-striated. Xylem. The xylem is composed of vessels, wood parenchyma, and wood fibres. Vessels. The vessels are rounded in outline and few in number. Wood Parench]rnia. The wood parenchyma cells are variable in size and shape, but all the cells are angled in outline. Medullary Rays. The medullary ray cells are not clearly distinguishable. Pith Parench]rnia. The pith parenchyma cells of the centre of the root resemble the cortical parenchyma cells. That the structure of rhizomes is similar to the structure of roots is shown by the drawings of spigelia rhizome (Plate 91), and by ruellia rhizome (Plate 92). CROSS-SECTION SPIGELIA RHIZOME The cross-section of spigelia rhizome (Plate 91) is as follows: Epidermis. The epidermal cells are nearly angled and free of cell contents. Cortex. The cortical parenchyma cells are usually slightly tangentially elongated. The cells of the outer layers are larger than the cells of the inner layers. Phloem. The phloem contains sieve cells and phloem parenchyma. The sieve cells are small, angled cells with thin, white walls. The phloem parenchyma cells resemble the sieve cells, but they are larger. Cambium. The cambium cells are rectangular, and they are CKOSS-SBCTION of RHIZOHB of SPIGELIA UARVlANDICAi^ L. I. Efridemiis. a. Cortical parenchyma. 3. Phloem. 4. Carobiuni. 5. Xylem. 6. Internal phloem. 7. Pith with itarch. Cboss-Sechon of Rhizome of Rhellia ciliosa, Pursh. , Epidermii. 7. CystoHth. 3. Stone cell. 4. Cortical parenctiyma. S. Bast fibres, 6. Pericyele. 7. Xylem. 8. Pith. 226 HISTOLOGY OF MEDICINAL PLANTS usually not dearly seen because the walls are partially collai^ed. Xj^em. The zylem is composed of vessels, wood parenchyma, medullary rays, and pith parenchyma. Vessels. The vessels are slightly angled in outline and few in number. Wood Parenchyma. The wood parenchyma cells are small and angled. Medullary Rays. The medullary ray cells are tangentially elongated, but in structure resemble the wood parenchyma cells. Pith Parenchyma. The pith parenchyma cells are rounded in outline and contain small, simple, rounded starch grains. CROSS-SECTION RUELLIA BHIZOME The cross-section of ruellia rhizome (Plate 92) differs from the structure of spigelia rhizome. It is as follows: Epidermis. The epidermal cells vary in shape from nearly square to oblong, and they are filled with dark-brown cell contents. Cortex. The cortex contains parenchyma and stone cells. The outer layer of the cortical parenchyma cells are variable in size and many of the cells contain deposits of calcium car- bonate and dark cell contents; the inner parenchyma cells are larger and they are free of the dark-brown cell contents, but many of the cells contain deposits of calcium carbonate. Stone cells with thick, white, porous, and striated walls occur in among the cortical parenchyma cells. Phloem. The phloem contains sieve cells, phloem, paren- chyma, and bast fibres. The sieve cells are small and with thin, white, angled walls. The phloem parenchyma cells resemble the sieve cells, but they are larger. The bast fibres occur singly or in groups of two or three. The walls are white, non-porous, and non-striated. Cambium. The cambium layer is composed of rectangularly shaped cells, which are frequently obliterated. Xylem. The xylem contains vessels, wood parenchyma, and medullary rays. The vessels are large, rounded cells with thick walls. ROOTS AND RHIZOMES 227 The wood parenchyma consists of thick- walled cells of irreg- ular size and form. The medullary rays are tangentially elongated and rectangular in form. Pith parench]rina« The pith parenchyma cells are rounded in outline and as large as the cortical parenchyma cells. POWDERED PINK ROOT When the roots and rhizomes of spigelia are powdered (Plate 93) they show the following structure: The epidermal cells are small and brownish on surface view, varying in size from 13 by 18 micromillimeters to 31 by 40 micromillimeters. When associated with parenchyma they ap>- pear as black masses. The cortical parenchyma cells are rounded and vary in size from 23 by 26 micromillimeters to 37.5 by 90 micromillimeters. Many of the cells from the root contain larger quantities of minute single rounded starch grains varying in size from i micromillimeter to 4 micromillimeters. The larger round single starch grains are found in both the cortical and pith parenchyma of the rhizome. They vary in size from 5 micromillimeters to 18 micromillimeters. The conducting elements are pitted tracheids varying from 10 micromillimeters to 38 micromillimeters in diameter. A few pitted and annular vessels are also found. The only fibres occurring are found in the xylem. They are not a prominent feature of the powder, as their walls break up into minute fragments. The pith parenchyma varies in size from 13 by 19 micromillimeters to 75 by 82.5 micromillimeters. It is in these cells that the largest starch grains occur. Distinguishing diagnostic characters of the powder: 1. Parenchyma with starch. 2. Dark masses of epidermal tissue. 3. Spigelia should contain starch, and it should not contain cystoliths, stone cells, or long, white-walled bast fibres. POWDERED RUELLIA ROOT When the roots of ruellia root and rhizome are powdered (Plate 94) they show the following structure: The epidermal cells vary from 7.8 by 15.6 micromillimeters Powdered Shgelia uabylandica, L. 1. Epidermia and cortical parenchyma. 3. Tracheids snd fibm. 3. Par- enchyma cells of the root containing the small starch grains, lon^tudinal view. 4. Parenchyma of the rhizome containing the large starch grains, transverse view. 5. Tracheids. 6. Surface view of the epidermal cells. 7. Starch scattered through the field, S and 8'. Dark masses of epidemul and underiying tissue. Powdered Ruellia ciliosa, Furah. I. Short, broad cystolithg from the rhizome, l'. Long cyatoliths from the root. 3 and 3'. Long, narrow, white-walled bast fibres. 3. Trachea] tissue from the xylem of the stem. 4. Root parenchyma. 5. Tracheal tissue from the xylem of the root. 6, Cortical parenchyma cells from the rhizome with short, broad cystoliths. 7 and 7'. Long, Ihick-walled aclerids from the root. 8. Short, broad aclerids from the stem. 9. Pitted pith parenchyma from the ■tern with intercellular space. 10. Parenchyma of the root with sclerid and cystolith, loi^tudinal view. 230 HISTOLOGY OF MEDICIXAL PLANTS to 1 5. 1 by 16.6 micromillimeters. The ceU contents are dark and the walls are lig^t. A few rows of the outer OHtkal paren- chyma cells of both the rhizome and the root have daLik cell contents and white walls. The dark contents disappear toward the phloem. The cortical cells vary from 13.6 by 14.3 micro- millimeters to 89.5 by 90.9 micromillimeters. In the cortical parenchyma cells of the rhizome are found the short, broad cystoliths measuring up to 52 by 62 micromillimeters. In the corresponding cells of the root are found the long, narrow c>-sto- iiths which measure up to 68.4 by 187.2 micromillimeters. Scattered throughout the powder are seen three distinct tjpes of sclcrids (stone cells) which are associated with the cortical parenchyma of both the stem and the root. Most of them are found, however, in the roots. First, the short, broad stone cells from the stem basis have square ends; the walls vary from 13 to 19.5 micromillimeters in thickness with branching pores which extend toward the adjacent cell. These sclerids varj^ in size from 52 by 54.6 micromillimeters to 45 by 130 micromilli- meters. Secondly, the long stone cells from the root vary from 32 by 96 micromillimeters to 45.5 by 542.5 micromillimeters with walls 16 micromillimeters thick. The width of the cell and the thickness of the wall vary but little throughout their entire length. The third type of stone cell also from the root has unequally thickened walls and the ends are square or blunt. A few long, narrow, colorless, thin-walled bast fibres also occur. They arc 13 micromillimeters wide, with walls 3.9 micromilli- meters thick. Annular spiral and pitted vessels are also found scattered throughout the powder. The diagnostic characters of the powder are: I. The short, broad, and long, narrow cystoliths. 3. The short, broad, and long, narrow sclerids. 3, The long, narrow, thin, white-walled bast fibres. In ix>ko rtH)t, ijKcac, sarsaparilla, and veratnmi are raphides. In belladonna and horse-nettle roots are micro-crystals. In calumba, stillingea, krameria, licorice, scamony root are prisms. In sa[H>naria, jalap, althea, spikenard, rumex, rhubarb are n>sette cr>'stals. In pleurisy roots both prisms and rosettes iKCur* In gentian, senega » s\inph'tuns, lovage, parsley, inula, ROOTS AND RHIZOMES 231 echinacea, angelica, burdock, and chicory no crystals of any kind occur. Root hairs occur in cross-sections of sarsaparilla root and false unicorn, but with these exceptions: root hairs do not occur on roots, because the younger part of the root with root hairs is not removed from the soil when the drug is collected. In sarsaparilla root there are several layers of hypodermal cells; in most roots there are no hypodermal cells. In the non-woody roots or the roots of herbs the parenchyma cells form the greater part of the tissues of the root. In ruellia root are stone cells; in spigelia root and many other roots there are no stone cells. In ruellia root are bast fibres; in spigelia, gentian, ipecac, chicory, dandelion, Symphytum, and lovage no bast fibres occur. In all the woody roots there is a periderm consisting of typical cork cells, as in black haw; or stone cells, as in asclepias; or of a mixture of lifeless parenchyma, medullary rays, etc., as in Oregon grape root. Woody roots have a phellogen layer which is absent in the non-woody roots. The nmnbers of layers of cortical parenchyma differ in the same root according to its age, but for a given root there is a normal variation. The niunber of layers of cortical parenchyma in proportion to other cells is less in woody roots. In woody roots there is no endodermis. The cambium in these cases shows clearly between the phloem and the xylem part of the fibro-vascular bundle. In woody roots the wood fibres are well developed and form a large part of the root, and the medullary rays have pitted side and end walls. The description given above of ruellia root is not typical of all roots, but the structure represents the greater number of the elements that it is possible to find in a root. In many roots, for instance, there are no stone cells, in others no epidermis and no endodermis. In asclepias, aconite, and calumba stone cells occur. In Symphytum, chicory, dandelion, burdock, elecam- pane, pyrethrum, gentian, and senega no stone cells occur. In aconite, althea, asclepias, belladonna, bryonia, columba, ipecac, jalap, krameria, sarsaparilla, scamony, stillingea, and rumex are characteristic starch grains. Symphytum, chicory, dande- 232 wrsTOUiGT or muhi ix\i puons Boa. burdock, tin Jiinamc, and pgrretlinnii contam i miKn^ but DO sfarrft In saipaossB. gfHtun. and ^^«^ wwithf^ starch nor mumi ocnxis. When itudviug roots die natsze ai the cpidennfe or the pexidexm mnst be ooosidemL as abo die wmnl^T of layers of cortical porcDciiTina; tbe occurrence, dtslrilwitiop, and amount oc stooe ceQs wfaen present: tbe presence or absence of the csdodencis; tbe oocnrrcnce and stmctme ai bast fibres when pnesezLt: the natnre oc the famhrom cells; the width and struc- ture oc the medullary rays, the size ai the wood fibres and wood parenchyma, and the nature oc the cdl oootents and the ar- rangement oc the fibro-vascular handle. CHAPTER n STEMS When studying stems it should first be determined whether they were derived from monocotyledonous or dicotyledonous plants. This fact is ascertained by determining the type of the fibro-vascular bundle. See Chapter XI. The next fact to determine is whether the stem is from an herb or from a woody plant. This fact is readily determined because herbaceous stems have a true epidermis, masses of collenchyma at the angles of the stem. The cortical cells contain chlorophyll, and the pith is very large. Woody stems have a corky layer, a phellogen layer, and the pith is very small except in the very young woody stems. Having determined these facts, a study should be made of the arrangement, form, structure, color, and the cell contents of the different cells in order to determine the species of plant from which the stem was obtained. HERBACEOUS STEMS The great variation in the structure of herbaceous stems is shown in the cross-sections of spigelia (Plate 95); in ruellia (Plate 96); in the charts of powdered genuine horehound, powdered spurious horehound, and in the chart of powdered insect flower stems. CROSS-SECTION SPIGELIA STEM Spigelia stem (Plate 95) has the following characteristic structure: Epidermis. The epidermal cells are papillate. Cortex. The cortical parenchyma cells consist of tan- gentially elongated cells which are oval in outline. Phloem. The phloem consists of sieve cells, phloem paren- chyma, and of bast fibres. 233 ':- > V ' • 4 le epicerrri*. parersch>ina. >rzM :• 5?:gell\ ma&ylandica. L. a. Phloern. 7. Inner phloem. 5. CArnbium. S. Pith. 6. XvJem. STEMS 235 The sieve cells are small, and with thin, white, angled walls. The phloem parenchyma resembles the sieve cells, but they are larger. The bast fibres are rounded in outline and the walls are thick, white, non-porous, and non-striated. Cambium. The cambium cells are rectangular in shape or the walls are collapsed and the cells indistinct. Xylem. The xylem contains vessels, wood parenchyma, medullary rays. The vessels are small and angled, the walls are thick and white. Wood parenchyma. The cells are variable in size and shape, and the walls are thick. The medullary ray cells are small, narrow, and tangentially elongated. Internal Phloem. External to the pith parenchyma are isolated groups of internal phloem consisting of sieve cells. Pith Parenchyma. The pith parenchyma cells are oval in form and irregularly placed. The cells contain small, simple starch grains. RUELLIA STEM The cross-section of ruellia stem (Plate 96)