William James Mansfield

“ The wall of the root hair acts like an osmotic membrane. The less dense watery solution outside the root hair passes through its wall and into the denser cell sap solution. As the solution is absorbed, it passes from the root hair into the adjoining cortical parenchyma cells.
It is a fact that root hairs are seldom found in abundance on medicinal roots. This is due to the fact that root hairs occur only on the smaller branches of the root, and that when the root is pulled from the ground the smaller roots with their root hairs are broken off and left in the soil. ”

“ The association of several organs in one form makes an organism. The oak-tree is an organism. It is made up of organs known as flowers, leaves, stems, roots, etc. Each of these organs is in turn made up of several kinds of tissue. In some cases it is difficult to designate a single function to an aggregation of cells (tissue) . In fact, a tissue may perform different functions at different periods of its existence or it may perform two functions at one and the same time; as an example, stone cells, whose primary function is mechanical, in many cases function as storage tissue. ”

“ Vessels are distinguished from other cells by their arrangement, by their large size when seen in cross-section, and by the thickening of the wall when seen in longitudinal sections of the plant or in powders. The side walls of vessels are thickened in a number of striking yet uniform ways. The chief types of thickening of the wall, beginning with one that is the least thickened, are annular, spiral, sclariform, pitted, and pitted with bordered pores. ”

“ The structure and composition of the wall of any given cell vary according to the ultimate function of the cell. The walls may be thin or thick, porous or non-porous, and colored or colorless. The composition of cell walls varies greatly. The majority of cell walls are composed of cellulose, in other cells of linin, in others of cutin, and in still others of suberin, etc. In the majority of cells the walls are laid down in a series of layers one over the other by apposition, similar to the manner of building a pile of paper from separate sheets. ”

“ The medullary ray cells are the lateral conducting cells of the plant. They conduct outwardly the water and inorganic salts brought up from the roots by the vessels and tracheids; and they conduct inwardly toward the centre of the stem the food material manufactured in the leaves and brought down by the sieve cells. The medullary rays thus distribute the inorganic and organic food to the living cells of the plant, and they conduct the reserve food material to the storage cells, and, lastly, they function in certain plants as storage cells. ”

“ As the trees and shrubs increase in diameter, cracks or fissures occur in the periderm, or corky layer. In such cases the phellogen cells divide and redivide in such manner as to cut off a portion of the parenchyma cells, stone cells, and fibres of the cortex which is inside of and below the fissure. All the parenchyma cells, etc., exterior to the newly formed cork cells soon lose their living-cell contents, since their food-supply is cut off by the impervious walls of the cork cells. ”

“ Latex tubes function both as storage and as conducting cells. They, like the sieve tubes, contain proteid substances chiefly, yet frequently starch is found. The cells bordering the latex tubes absorb from them, as needed, the soluble food material. While our knowledge concerning the function of latex in some plants is meagre, still in other plants it is practically certain that the latex is composed of nutritive substances which are utilized by the plant as food. In certain other plants the latex appears to be used as a means of resisting insect attacks and as a protection against injury. ”

“ In many xerophytic terrestrial plants, the trichomes occurring on leaves act as a water-absorbing tissue. In such plants the walls of the hairs are composed largely of cellulose. It is obvious that these hairs absorb the water of condensation caused by dew and light rains—water which could not reach the plant except by such means.
There is no special tissue set aside for the absorption of gases from the air. Carbon dioxide, which contributes the element carbon to the starch formed by photosynthesis, enters the leaf by way of the stoma and lenticels. ”

“ In order to bring out the structure of the protoplast (living part of the cell) , it will be necessary to begin with the living part of the plant and to use the long paraffin method or the collodion method.
Small fragments of a leaf, stem, or root-tip are placed in chromic-acid solution, acetic alcohol, picric acid, chromacetic acid, alcohol, etc., depending upon the nature of the specimen under observation. ”

“ Collenchyma cells differ from parenchyma cells in a number of ways: first, the cell cavity is smaller; secondly, the walls are thicker, the greater amount of thickening being at the angles of the cells—that is, the part of the cell wall which is opposite the usual intercellular space of parenchyma cells, while the wall common to two adjoining cells usually remains unthickened. In horehound stem (Plate 30, Fig. 2) the thickening is so great at the angles that no intercellular space remains. ”

“ The mechanical tissue of the stem is arranged in the form of solid or hollow columns in order to sustain the enormous weight of the branches. In roots the mechanical tissue is combined in ropelike strands, thereby effectively resisting pulling stresses. The epidermis of leaves subjected to the tearing force of the wind has epidermal cells with greatly thickened walls, particularly at the margin of the leaf. The epidermal cells of most seeds have very thick and lignified cell walls, which effectively resist crushing forces. ”

“ The endodermal cells of sarsaparilla root (Plate 35, Fig. 1) are never more than one layer in thickness. The walls are porous and of a yellowish-brown color. Alternating with the thick-walled cell is a thin-walled cell, which is frequently referred to as a passage cell.
The endodermal cells of triticum (Plate 35, Fig. 2) are yellowish, and the walls are porous and striated. There are one or two layers of cells. The cells forming the outer layer have very thin outer but thick inner walls, while the cells forming the inner layer are more uniform in thickness. ”

“ The inner lenses of the eye-pieces and the under lens of the Abbé condenser should occasionally be cleaned. The mechanical parts of the stand should be cleaned if dust accumulates, and the movable surfaces should be oiled occasionally. Never attempt to make new combinations of the ocular or objective lenses, or transfer the objectives or ocular from one microscope to another, because the lenses of any given microscope form a perfect lens system, and this would not be the case if they were transferred. ”

“ The crystals are nearly perfect cubes and occur singly (5) or in groups (6) . On the longitudinal section of the bark the crystals occur in parenchyma cells surrounded by a reddish cell content and form parallel rows which are very characteristic. The resin occurs either as white, angled fragments (7) in a water mount, or as globular mass (8) or as reddish-brown pieces (10) . The starch is very abundant and is distributed through the field. The diagnostic grain is lens-shaped, with a cleft hilum, which is nearly straight, or slightly curved, and runs parallel to the long diameter of the grain. ”

“ The walls of collenchyma consist of cellulose.
STONE CELLS
Stone cells, like bast fibres, are branched or non-branched. Each group is then separated into subgroups according to wall structure (whether striated, or pitted and striated, etc.) , thickness of wall and of cell cavity, color of wall and of cell contents, absence of color and of cell contents, etc.
BRANCHED STONE CELLS
Branched stone cells occur in a number of drugs. In witch-hazel bark (Plate 31, Fig. 2) the walls are thick, white, and very porous. In some cells the branches are of equal length; in others they are unequal. ”

“ The most important of the different types of storage tissue that occurs in plants are the storage cells, the storage cavities, and the storage walls.
STORAGE CELLS
Several different types of cells function as storage tissue. These cells, which are given in the order of their importance, are parenchyma, crystal cells, medullary rays, stone cells, wood fibres, bast fibres, and epidermal and hypodermal cells. ”

“ The pith cells in the stems of many herbs become torn apart during the growth of the stem, with the result that large irregular cavities are formed. These cavities are usually filled with circulatory air.
In the stems of conium, cicuta, angelica, and other larger herbaceous stems the pith separates into layers. When a longitudinal section is made of such a stem it is seen to be composed of alternating air spaces and masses of pith parenchyma.
The intercellular spaces are very large in leaves where enormous quantities of carbon dioxide are vitalized in photosynthesis. ”

“ In chimaphila and uva-ursi there are no outgrowths from the epidermal cells.
In senna, witch-hazel, chestnut, and coca, numerous non-glandular hairs occur on the epidermis. In tobacco, belladonna, henbane, pennyroyal, peppermint, and spearmint both glandular and non-glandular hairs occur on the epidermis.
When studying leaves there should be considered the absence or presence of outgrowths and their nature; the nature of the epidermis and, when present, the number of layers of the hypodermis; the nature of the stoma, whether raised above, even with, or below the level of the epidermis ”

“ The barks of certain plants have characteristic stone cells, while in many other barks no stone cells occur. Many leaves have characteristic trichomes; others are free from trichomes, etc. [58] Yet all cells performing a given function will structurally resemble each other. In the present work the nucleus and other parts of the living protoplast will not be considered, for the reason that these parts are not in a condition suitable for study, because most drugs come to market in a dried condition, a condition which eliminates the possibility of studying the protoplast. ”

“ All multicellular plants are built up by the repeated cell division of one original cell. If the cells formed are similar in structure and function, they form a tissue. In multicellular plants many different kinds of tissues will be formed as a result of cell division, since there are many different functions to be performed by such an organism. ”

“ It is an interesting fact that the spiral thickening in conducting cells is usually separate from the side wall and nearly always appears as indicated at 5. An occasional rosette crystal of calcium oxalate (6) is seen in the field. The wood parenchyma (7) , which makes up a very small percentage of the xylem, is not readily found in the powder. The pith parenchyma cells (8) have thick, porous side walls and perforated side walls. The wood fibres (9) usually occur in masses surrounding the conducting cells; when occurring singly, the oblique pores readily distinguish them from the bast fibres. ”

“ The organic cell contents include plastids, starch grains, mucilage, inulin, sugar, hesperidin, alkaloids, glucocides, tannin, resin, and oils.
CHLOROPHYLL
The chloroplasts of the higher plants are green, and they vary somewhat in size, but they have a similar structure and form.
Chloroplasts are mostly oval in longitudinal view and rounded in cross-section view. Each chlorophyll grain has an extremely thin outer wall, which encloses the protoplasmic substance, the green granules, a green pigment (chlorophyll) , and a yellow pigment (xanthophyll) . ”

“ In microscopical drug analysis the presence of hairs is always noted, and in many cases the purity of the powder can be ascertained from the hairs. Botanists seem to have given little attention to the study of plant hairs. This accounts for the fact that information concerning them is very meagre in botanical literature, and, as far as the author can learn, no one has attempted to classify them. In systematic work, plant hairs could be used to great advantage in separating genera and even species. Hairs are, of course, a factor now in systematic work. ”

“ The cells of the middle layer of flower petals, like the mesophyll of leaves, is loosely arranged owing to the peculiar branching form of the cells.
Seeds and fruits contain, as a rule, few or no intercellular spaces. ”

“ There is no other element in powdered drugs which is of so great a diagnostic value as the plant hair. The same plant will always have the same type of hair, the only noticeable variation being in the size. ”