CHAPTER Vm (Part 2)

belladomia root (Plate 75, Fig. 2) the compoimd grains are more nimierous; while in sanguinaria the simple grains are more nimierous, etc. OUTLINE The outline of starch grains is made up of (i) roimded, (2) angled, and (3) rounded and angled surfaces. Starch grains with rounded surfaces may be either spherical, as in Plate 74, Fig. 3, or oblong or elongated, as in Plate 71, Fig. I. Other starches with rounded surfaces are shown on Plates 72 and 73. Angled outlined grains are common to cardamon seed, white pepper, cubebs, grains of paradise (Plate 76, Fig. 4), and to com (Plate 70, Fig. 3). The outlines of all compound grains are made up partly of plane and partly of curved surfaces. SIZE The size (greatest diameter) of starch varies greatly even in the same species, but for each plant there is a normal variation. In spherical starch grains the size of the individual grains is invariable, but in elongated starch grains and in parts of com- poimd grains the size will vary according to the part of the grain measured. In zedoary starch (Plate 71, Fig. 4), for instance, the size will vary according to whether the end^ side, or surface of the starch grain is in focus. The parts of compound grains often vary greatly in size. Such a variation is shown in Plate 75, Fig. 2. HILX7M The hilum is the starting-point of the starch grain or the first part of the grain laid down by the amyloplast. The hilum will be central if formed in the middle of the amyloplast, and excentral if formed near the surface of the amyloplast. It has been shown that the developing starch grain with eccentric hilum usually extends the wall of the amyloplast if it does not actually break through the wall. Starch grains with excentral hilums are therefore longer than broad. 184 HISTOLOGY OF MEDICINAL PLANTS cell sap, and is conducted to all parts of the plant. The sugar not utilized in cell metabolism is stored away in the form of reserve starch or starch grains by colorless plastids or amyloplasts. The amyloplasts change the sugar into starch by extracting a molecule of water. This structureless material (starch) is then formed by the amyloplast into starch grains having a definite and characteristic form and structure. Starch grains vary greatly in different species of plants, owing probably to the variation of the chemical composition, density, etc., of the protoplast, and to the environmental con- ditions under which the plant is growing. OCCURRENCE Starch grains are simple, compound, or aggregate. Simple starch grains may occur as isolated grains (Plates 70, 71, and 72), or they may be associated as in cardamon seed, white pepper, cubeb, and grains of paradise, where the simple grains stick together in masses, having the outline of the cells in which they occur. These masses are known as aggregate starch. Aggregate starch (Plate 76) varies greatly in size, form, and in the nature of the starch grains forming the aggregations. Compound starch grains may be composed of two or more parts, and they are designated as 2, 3, 4, 5, etc., compound (Plate 7s). The parts of a compound grain may be of equal size (Plate 75 1 Fig. 4), or they may be of unequal size (Plate 75, Fig. 2). In most powders large numbers of the parts of the com- pound grains become separated. The part in contact with other grains shows plane surfaces, while the external part of the grain has a curved surface. There will be one plane and one curved surface if the grain is a half of a two-compound grain; two plane and one curved surface if the grain is a part of a three- compound grain, etc. The simple starch grains forming the aggregations become separated during the milling process and occur singly, so that in the drugs cited above the starch grains are solitary and aggregate. Many plants contain both simple and compound starch grains (Plate 74, Fig. 3). CELL CONTENTS 185 In some forms — e.g., belladomia root (Plate 75, Fig. 2) the compoimd grains are more numerous; while in sanguinaria the simple grains are more numerous, etc. OUTLINE The outline of starch grains is made up of (i) roimded, (2) angled, and (3) rounded and angled surfaces. Starch grains with rounded surfaces may be either spherical, as in Plate 74, Fig. 3, or oblong or elongated, as in Plate 71, Fig. I. Other starches with rounded surfaces are shown on Plates 72 and 73. Angled outlined grains are common to cardamon seed, white pepper, cubebs, grains of paradise (Plate 76, Fig. 4), and to corn (Plate 70, Fig. 3). The outlines of all compound grains are made up partly of plane and partly of curved surfaces. SIZE The size (greatest diameter) of starch varies greatly even in the same species, but for each plant there is a normal variation. In spherical starch grains the size of the individual grains is invariable, but in elongated starch grains and in parts of com- pound grains the size will vary according to the part of the grain measured. In zedoary starch (Plate 71, Fig. 4), for instance, the size will vary according to whether the end^ side, or surface of the starch grain is in focus. The parts of compound grains often vary greatly in size. Such a variation is shown in Plate 75, Fig. 2. HILX7M The hilum is the starting-point of the starch grain or the first part of the grain laid down by the amyloplast. The hilum will be central if formed in the middle of the amyloplast, and excentral if formed near the surface of the amyloplast. It has been shown that the developing starch grain with eccentric hilum usually extends the wall of the amyloplast if it does not actually break through the wall. Starch grains with excentral hilums are therefore longer than broad. '^<^ i '^'o Stabch I, CaUbar bean {Phys)}stig;ma ventnosum, Balfour). 3. Marsh mallow root (AUHaa o^cinaHs, L.). 3, Field com (Zta mays, LO. Starch I. Galanga root (Alptma oficinarum Hance). a. Kola nut (CtAa vera, [K.] Schum ) 3 Geranium rhixomc {Geramum macidotum, L.). 4. Zedoary root {Curcuma Kdoana Rose ) ^ A Surface view of starch graio. 4-B. Side \iew of starch grain. 4 C. End view of starch grain. 188 HISTOLOGY OF MEDICINAL PLANTS In central hilum starch grains the grain is laid down around the hilum in the form of concentric layers. These layers are of variable density. The dense layers are formed when plenty of sugar is available, and the less dense layers are formed when little sugar is available. The unequal density of the different layers gives the striated appearance characteristic of so many starch grains. In eccentric hilum starch grains the starch will be deposited in layers which are outside of and successively farther from the hilum. The term hilum has come to have a broader meaning than formerly. Hilum includes at the present time not only the starting-point of the starch grain, but the fissures which form in the grain upon drying. In all cases these fissures originate in the starting-point, hilum, and in some cases extend for some distance from it. The hilum, when excentral, may occur in the broad end of the grain, galanga, and geranium (Plate 71, Figs. I and 3), or in the narrow end of the grain, zedoary (Plate 71, Fig. 4). NATURE OF THE HILUM The hilum, whether central or excentral, may be rounded (Plate 75, Fig. i); or simple cleft, which may be straight (Plate 71, Fig. i); or curved cleft (Plate 71, Fig. 2); or the hilum may be a multiple cleft (Plate 74, Fig. 3). In studying starches use cold water as the moimting mediiun, because in cold water the form and structure are best shown, and because there is no chemical action on the starch. On the other hand, the form and structure will vary considerably if the starch is mounted in hot water or in solutions of alkalies or acids. The hilum appears colorless when in sharp focus, and black when out of focus. Starch grains, when boiled with water, swell up and finallv disintegrate to form starch paste. Starch paste turns blue upon the addition of a few drops of weak lugol solution. Upon heating, this blue solution is de- colorized, but the color reappears upon cooling. If a strong solution of lugol is used in testing, the color will be bluish black. Starch . Orris root {Iris fiorentinia h.). :. Stillingea root (SliUitigea sylcalka, L.). i. Calumba root {Jaleorhita paltnala, ILam PLATE 73 ^ 6 I Stakcu 1 . Male fern (Dryopteris margincUis, [L.] A. Gray). 2. African ginger (Zingiber officinalis, Rose). 3. Yellow dock {Rumex crispus, L.). 4. Pleurisy root (Asdepias tuberosa, L.). /""^ ^^.o F i -"^ w .^v O Starch . Kava-kava (Piper melkyiticum, Forst., f.). . Pokeroot (Phytolacca amerieana, L.). . Rhubarb (Rheum officinale. Baill.). PLATE 75 Starch Grains 1. Bryonia (Bryonia alba, L.)- 2. Belladonna root (Atropa belladonna, L.). 3. Valerian root (Valeriana officinalis, L.). 4. Colchicum root (Colchicum autumnale, I..V Stakch Masses I. Aggregate starch of cardamon seed [EUUaria cardamomum, Maton). a. Aggregate starch of white pepper {Piper ntgrum, L,). 3. Aggregate starch of cubebs [Piper cubeba, L., f.). A. Aggregate starch of grains of paradise (Amamum meiegiuUa, Rose.). 194 HISTOLOGY OF MEDICINAL PLANTS INULIN Inulin is the reserve carbohydrate material found in the plants of the composite family. The medicinal plants containing inulin are dandelion, chicor% elecampane, pyrethrum, and burdock. Plate 77, Figs, i and 2 show masses of inulin in dandelion and pyrethrum. In these plants the inulin occurs in the form of irregular, structureless, grayish-white masses (Plate 77). In powdered drugs inulin occurs either in the parenchyma cell or as irregular isolated fragments of variable size and form. Inulin is structure- less and the inulin from one plant cannot be distinguished microscopically from the inulin of another plant. For this reason inulin has little or no diagnostic value. The presence or absence of inulin should always be noted, however, in examin- ing powdered drugs, because only a few drugs contain inulin. When cold water is added to a powder containing inulin it dissolves. Solution will take place more quickly, however, in hot water. Inulin occurs in the living plant in the form of cell sap. If fresh sections of the plant are placed in alcohol or glycerine, the inulin precipitates in the form of crystals. MUCILAGE Mucilage is of common occurrence in medicinal plants. Characteristic mucilage cavities filled with mucilage occur in sassafras stem (Plate 66, Fig. 2), in elm bark (Plate 66, Fig. i), in althea root, in the outer layer of mustard seed, and in the stem of cactus grandiflorus. In addition, mucilage is found associated with raphides in the cr>'stal cells of sarsaparilla, squill, false imicom, and polygonatum. When drugs containing mucilage are added to alcohol, glycerine, and water mixture, the mucilage swells slightly and becomes distinctly striated, but it will not dissolve for a long time. Refer to Plate 79, Fig. 6. Mucilage, when associated with raphides, swells and rapidly dissolves when added to alcohol, glycerine, and water mixture. The mucilage is, therefore, different from the mucilage found in mucilage cavities, because it is more readily soluble. In coarse-powdered bark and other mucilage containing CD Inulin (iHuia kdenium, L.) I. Inulin in the parenchyma cells of dandelion root. 3. Inulin from Roman pyrethrum root {Anacyclus pyretkrum. {L.) D. C). 196 HISTOLOGY OF MEDICINAL PLANTS drugs the mucilage masses are mostly spherical or oval in outline (Plate 66, Figs. 2 and 3) the form being similar to the cavity in which the mass occurs. Acacia, tragacanth, and India gum consist of the dried mucilaginous excretions. HESPERIDIN Hesperidin occurs in the epidermal cells of short and long buchu. It is particularly characteristic in the epidermal cells of the dried leaves of short buchu. In these leaves the hesperidin occurs in masses which resemble rosette crystals (Plate 54, Fig. i). Hesperidin is insoluble in glycerine, alcohol, and water, but it dissolves in alkali hydroxides, forming a yellowish solution. VOLATILE OILS Volatile oils occur in cinnamon stem bark, sassafras root bark, flowers of cloves, and in the fruits of allspice, anise, feimel, caraway, coriander, and cumin. In none of these cases is the volatile oil diagnostic, but its presence must always be determined. When a powdered drug containing d volatile oil is placed in alcohol, glycerine, and water mixture the volatile oil con- tained in the tissues will accumulate at the broken end of the cells in the form of roimded globules, while the volatile oil adhering to the surface of the fragments will dissolve in the mixture and float in the solution near the under side of the cover glass. Volatile oil is of little importance in histological work. TANNIN Tannin masses are usually red or reddish brown. Tannin occurs in cork cells, medullary rays of white pine bark (Plate 48, Fig. B), stone cells, and in special tannin sacs. The stone cells of hemlock and tamarac bark and the medul- lary rays of white pine and hemlock bark contain tannin. Tannin associated with prisms occurs in tannin sacs in white pine and tamarac bark. These sacs are frequently several millimeters in length and contain a great number of crystals surroimded by tannin. CELL CONTENTS 197 Deposits of tannin are colored bluish black with a solution of ferric chloride. ALEURONE GRAINS Aleurone grains are small granules of variable structure, size, and form, and they are composed of reserve proteins. They occur in celery, fennel, coriander, and anise, fruits, in sesame, sunflower, curcas, castor oil, croton oil, bitter almond, and other oil seeds. In many of the seeds the aleurone grains completely fill the cells of the endosperm, embryo, and peristerm. In wheat, rye, barley, oats, and com the aleurone grains occur only in the outer layer or layers of the endosperm, the remaining layers in these cases being filled with starch. In powdered drugs the aleurone grains occur in parenchyma cells or free in the field. STRUCTURE OF ALEURONE GRAINS Aleurone grains are very variable in structure. The simplest grains consist of an undifferentiated mass of proteid substance surrounded by a thin outer menibrane. In other grains the proteid substance encloses one or more rounded denser proteid bodies known as globoids. In other grains a crystalloid — crystal- like proteid substance — is present in addition to the globoid. In some grains are crystals of calcium oxalate, which may occur as prisms or as rosettes. AH the different parts, however, do not occur in any one grain. In castor-oil seed (Plate 77a, Fig. 8) are shown the membrane (A), the ground mass (5), the crys- talloid (C), and the globoid (D). FORM OF ALEURONE GRAINS Much attention has been given to the study of the special parts of the aleurone grains, but one of the most important diagnostic characters has been overlooked, namely, that of comparative form. For the purposes of comparing the forms of different grains, they should be mounted in a medium in which the grain and its various parts are insoluble. Oil of cedar is such a medium. The variation in form and size of the aleurone grains when mounted in oil of cedar is shown in Plate 77a. 198 HISTOLOGY OF BIEDICINAL PLANTS DESCRIPTION OF ALEURONE GRAINS The aleurone grains of curcas (Plate 77a, Fig. i) vary in form from circular to lens-shaped, and each grain contains one or more globoids. The globoids are larger when they occur singly. In sunflower seed (Plate 77a, Fig. 2) the grains vary from reni- form to oval, and one or more globoids are present; many occur in the center of the grain. The aleurone grains of flaxseed (Plate 77a, Fig. 3) resemble in form those of sunflower seed, but the grains are uniformly larger and some of the grains contain as many as five globoids. In bitter almond (Plate 77a, Fig. 4) the aleurone grains are mostly circular, but a few are nearly lens-shaped. A few of the large, rounded grains contain as many as nine globoids; in such cases one of the globoids is likely to be larger than the others. The aleurone grains of croton-oil seed (Plate 77a, Fig. 5) are circular in outline, variable in form, and each grain contains from one to seven globoids. In sesame seed (Plate 77a, Fig. 6) the typical grain is angled in outline and the large globoid occurs in the narrow or con- stricted end. The aleurone grains of castor-oil seed (Plate 77a, Fig. 7) re-* semble those of sesame seed, but they are much larger, and many of the grains contain three large globoids. When these grains are mounted in sodium-phosphate solution, the crystal- loid becomes visible. TESTS FOR ALEURONE GRAINS Aleurone grains are colored yellow with nitric acid and red with Millon's reagent. The proteid substance of the mass of the grain, of the globoid, and of the crystalloid, reacts differently with different reagents and dyes. The ground substance and the crystalloids are soluble in dilute alkali, while the globoids are insoluble in dilute alkali. The ground substance and crystalloids are soluble in sodium phosphate, while the globoids are insoluble in sodium phosphate. Calcium oxalate is insoluble in alkali and acetic add, but it dissolves in hydrochloric acid. PLATE 770 •/'•••3 1.0 ^ ^ ^ # ^^® &' % * I a Aleurone Grains 1. Curcas {Jatropha curcas^ L.). 2. Sunflower seed {Hdianthus annuus, L.). 3. Flaxseed (Linum usitalissimum, L.). 4. Bitter almond {Prunus atnygdalus, amara, D.C.). 5. Croton-oil seed (Croton Hglium^ L.). 6. Sesame seed {Sesamum indicutn, L,), 7 and 8. Castor-oil seed (Ricinus communis, L.). 200 HISTOLOGY OF MEDICINAL PLANTS CRYSTALS Calcium oxalate crystals form one of the most important inorganic cell contents found in plants, because of the per- manency of the crystals, and because the forms common to a given species are invariable. By means of