The histological structure of flowers is readily seen in the powder; therefore, in studying flowers, it is not necessary to section the various parts. Each part of the flower should be isolated and powdered separately and each separated part studied. In each case the powders will contain surface, cross-, and radial sections of the parts powdered. While studying flowers, special attention should be given to the pollen grains, to the papillae of the petals, to the papillae of the stigma, and, in certain flowers, to the style tissue. In the composite flowers special attention should also be given to the involucre scales, to the scales of receptacle, and, when present, to the pappus. In addition, attention must be given to secretion cavities, as in cloves.<Callout type="tip" title="Tip">Proper isolation and powdering are crucial for accurate analysis.</Callout>
Pollen grains are one of the most characteristic elements found in powdered flowers, because they are so small that they are not broken up when the drug is milled. The two principal groups of pollen grains are, first, those with non-spiny walls (Plate 113); and, secondly, those with spiny walls (Plate 114), as shown in the two charts.<Callout type="important" title="Important">Identifying the type of pollen is essential for correct identification.</Callout>
In lavender flowers the pollen grains have six constrictions of the outer wall. This wall is slightly striated and the cell contents are granular. In clover flowers the pollen grains are mostly rounded in outline, the wall is uniformly thickened, and cell contents arc coarsely granular. In belladonna flowers the pollen grains terminate in three blunt points. In Spanish saffron the pollen grains are spherical and the cell contents are granular.<Callout type="risk" title="Risk">Misidentification of pollen can lead to incorrect medicinal use.</Callout>
Shooib- WALLED Pollen Gbains I. Cloves (Eugenia caryophyliata, Thunb.). 2. Santonica (Artemisia pauctfiora, Weber). 3. Elder (Samlnuus cana^tensis, L.)- 4- Century minor (Erythraa centaurium [L.|, Pers.). 5. Pichi (Fabiana imbrtcata, R. and P.). 6. Cyani. 7. Lavender (LavaTtduiaefficinalii, Chaix.). 8. Clover (Trifolium pralenst, L.)- 9. Belladonna (Alropa belladonna, L.). lo. Spanish saffron (Croau latima, L.).
Spiny Walled Pollen Grains I. Anthemis (Anihemis nobilis, L.). 3. Arnica {Arnica monlana. L.). 3. Calendula (Calendida qfficiniilis, L.). 4. Cassia flowers. 5. American saffrun {Carllmmus tinclorius, L. 6. Blue malva flowers (Maha syliestris, L,).
FLOWERS 273 The non-spiny- walled pollen grains differ not only in micro-scopic appearance, but also in size. Clove pollen grains are the smallest, while Spanish saffron pollen grains are the largest.<Callout type="beginner" title="Beginner">Understanding the differences in pollen grain size is key for identification.</Callout>
NON-SPINY-WALLED POLLEN GRAINS In cloves the pollen grains show a six-sided, angled cavity and an outer wall which terminates in three slightly pointed, narrowly notched portions, separated by nearly straight walls. In santonica the pollen grains have smooth, unequally thickened walls, which are strongly constricted at three points, the outline resembling three half-circles placed together. In elder flowers the pollen grains appear circular or three-parted. The wall is of nearly uniform thickness, even at the constricted part of the grain.<Callout type="gear" title="Gear">Microscope and proper powdering equipment are essential for accurate analysis.</Callout>
SPINY-WALLED POLLEN GRAINS In anthemis the pollen grains have unequally thickened walls constricted in three places. The spines are short, broad at the base, and sharp-pointed. In arnica flowers the pollen grains show three light-colored pores and numerous short spines. In calendula flowers the pollen grains show one or more pores, typically three pores. These pores appear as white spots, and the wall immediately over the pore is smooth and thinner than the remaining part of the wall ; the spines are very numerous.<Callout type="risk" title="Risk">Incorrect identification can lead to misapplication in medicine.</Callout>
In matricaria are numerous, greenish-brown, spiny-walled pollen grains. In anthemis are multiceDular, uniseriate non-glandular hairs with three or four short, broad, yellow-walled basal cells and a greatly elongated, thin, gray-walled apical cell. In arnica are multiseriated branched hairs of the pappus, and numerous large, yellowish, spiny-walled pollen grains.<Callout type="important" title="Important">Detailed examination is necessary for accurate identification.</Callout>
STIGMA PAPILLA The papillas of the stigma of most flowers form a characteristic element even when the flower is powdered. In the case of composite flowers the papillae of the disk and ray flowers differ. In American saffron the papillae of the style differ in a recognizable way from the papillae of the stigma.<Callout type="warning" title="Warning">Incorrect identification can lead to dangerous misapplication.</Callout>
The papillae of the stigma of the ray and disk flowers of arnica, anthemis, matricaria, and insect flowers differ greatly. Even the papillae of the stigma of the ray and disk flowers differ. In all cases observed the papillae of the ray flowers are smaller than the papillae of the disk flowers.<Callout type="important" title="Important">Detailed examination is necessary for accurate identification.</Callout>
The papillae of the stigma of saffron (Plate 115, Fig. 3) are long and tubular. These papillae are nearly uniform in diameter, and the apex is blunt and rounded. The wall is slightly granular in appearance. The papillae of the stigma of American saffron (Plate 116, Fig. 2) are short and tubular. Each papilla is broadest at the base and tapers to a slender point. The papillae of that part of the style which emerges from the corolla (Plate 116, Fig. i) are large and curved, and the walls are very thick. The apex of the papilla is frequently solid.<Callout type="risk" title="Risk">Misidentification can lead to incorrect medicinal use.</Callout>
The papillae of the stigma of the ray flowers of anthemis (Plate 117, Fig. i) have thin, slightly striated walls; while the papillae of the stigma of the disk flowers (Plate 117, Fig. 2) are longer, the walls are thicker, and the cell content is denser.<Callout type="important" title="Important">Detailed examination is necessary for accurate identification.</Callout>
The solitary hairs are divided into the branched and non-branching hairs.
POWDERED INSECT FLOWERS The microscopic examination of insect powder is difficult for the reason that there are so many elements to be constantly kept in mind. The parts of the flower which contribute characteristic cells are the stem, involucre, ray flowers, disk flowers, and the receptacle. In each of these parts there are many different types of cells.<Callout type="tip" title="Tip">Proper isolation and powdering are crucial for accurate analysis.</Callout>
There are practically two types of flowers found in insect powder of commerce: first, closed or immature flowers, and secondly, open or mature flowers. As explained above, the half-open flowers consist largely of the two above-named varieties. Let us first consider the structure of the closed insect flowers as illustrated in Plate 118.<Callout type="important" title="Important">Proper isolation and powdering are crucial for accurate analysis.</Callout>
The involucre has many characteristic cells. The more prominent ones seen in the powder are the edge of the scale with the attached hair (Fig. i). These hairs (Fig. 3) are T-shaped. The terminal cell is expanded laterally, and it terminates in two points. Connecting the terminal cell with the epidermis are two or three cells which are slightly longer than broad. In the powder the terminal cell is usually attached to fragments only of the supporting cells. Fibres of the bracts have thick, wavy, porous walls, and they have a tendency to occur in masses.<Callout type="gear" title="Gear">Microscope and proper powdering equipment are essential for accurate analysis.</Callout>
The upper epidermis (Fig. 4) of the ray-flower petal is prominently papillate. The under epidermis consists of wavy cells without papillae. Another view of the papillae is shown in Fig. 6. The parenchyma of the ray flowers (Fig. 7) contain cubical crystals. The lobe of the disk-flower petal (Fig. 8) is papillate at the end, the terminal cells have thick outer and thin inner walls.<Callout type="important" title="Important">Detailed examination is necessary for accurate identification.</Callout>
The filament tissue (Fig. 9) is composed of nearly square cells. The calyx tissue (Fig. 10) is made up of thin-walled cells with slightly papillate margins. The lobe of the stamen (Fig. 11) consists of nearly uniform epidermal cells which are in contact throughout their long diameter, while the hypodermal cells are thin-walled and angled.<Callout type="risk" title="Risk">Misidentification can lead to incorrect medicinal use.</Callout>
The pollen grains (Fig. 12) are dark yellowish green, thin, and the wall does not appear perforated by pores. The papillae of the stigma (Fig. 13) are clustered, club-shaped, and nearly white in color. They are usually found detached in the powder. All parts of the pistil contain secreting cells, but the most conspicuous secreting cavities (Fig. 14) are those of the ovary.<Callout type="important" title="Important">Detailed examination is necessary for accurate identification.</Callout>
The parenchyma of the receptacle occurs in fragments which have strongly marked porous walls.
OPEN INSECT FLOWERS Many of the structures of open insect flowers (Plate 119) are similar to those found in the closed flower. There is practically no difference in the edge of the scale (Fig. i); or the fibre of the scale (Fig. 2) ; or the T-shaped hairs (Fig. 3) ; or the upper epidermis of the ray flower (Fig. 4) ; or the under epidermis of the ray flower (Fig. 5) ; or the cross-section of the ray petal (Fig. 6) ; or the lobe of the disk petal (Fig. 7) ; or the filament tissue (Fig. 8) ; or the lobe of the stamen (Fig. 9) ; or the papillae of the stigma (Fig. 12); or the parenchyma of the receptacle (Fig. 15). The difference in structure is found, first, in the involucre scales, which are more fibrous than the scales of the closed flowers; secondly, in the pollen (Fig. 11), which is less abundant than in the closed flower; it is also lighter in color and usually shows the wall perforated by three pores; thirdly, the outer layers of the achene consist of thick, porous-walled stone cells (Fig. 13), which occur singly or in groups; fourthly,
Powdered Open Insect Flowers I. Edge of involucre scale. 2. Fibres of involucre scale. 3. Hairs. 4. Upper epidermis of ray flower. 5. Under epidermiB o( ray flower. 6. Ci-oss- section of ray petal. 7. Lobe of disk flower. 8. Filament tissue. 9. Lobe of stamen. 10. Calvxlissue. 11. Pollen. 12, Papillie of the stigma. 13. Stone cells from the acncnc and cross-section of achene. 14. Secretion cavity with surrounding cells. 15. Parenchyma of the receptacle.
A corr.Tr-oc aiiulterant fi-cnd la open insect flowers is the flower-heads of European fiic^y C.leuccintkemum). Examination Of powdered foTrers eip^jrted from Europe shows that the entire flower-head is zround ind with the insect flowers. In the cheaper varieties of •Dpen dowers, only the tubular flowers are added after they have been separated from the heads by crushing and sifting. These mbular flowers so closely resemble the tubular dowers of the true insect flowers that it is practically impossible to distinguish between them macroscopically. The quickest and surest way to identify them is to reduce a portion of the floweis to a fine powder and examine it microscopically.
Certain structures of the white daisies (Plate 120) are somewhat similar to those found in insect flowers. These structures are the papilbe of the ray petal ' Figs. 3, 5, and 13), the lobe of the disk petal 'Fig. 14 . and the lobe of the stamen and the pollen ^Fig. 8;. The differences are as follows: The under epidermis of the ray flowers is composed of way cells which are more elongated than the ray flowers of the under epidermis of the ray petal of insect flower. The filament tissue is made up of slightly beaded cells instead of smooth-walled cells. The papillae of the stigma are smaller than the [>apilke of insect flowers. The most striking difference is found in the structure of the achene. The epidermal tissue of the achene is composed of [>alisade cells (Fig. 10), which in the mature form have thick white walls and scarcely any cavity. These cells swell perceptibly when placed in water. The other striking feature of the achene is the bright red resin masses which occur free in the field. Even a small trace of daisies in insect powder can be identified.
When studying flowers there should be considered the number and structure of pollen grains; the nature of the papillae of the stigma and the petals; the nature of the hairs of the corolla and calyx, when present. In the composite flowers we should also consider the structure of the involucre scales, and, when present, the structure of the receptacle scales, as in the case of anthemus, and of the pappus hairs, as in the flowers of arnica, boneset, grindelia, and aromatic goldenrod.
Key Takeaways
- Proper isolation and powdering are crucial for accurate analysis.
- Identifying the type of pollen is essential for correct identification.
- Detailed examination is necessary to distinguish between similar structures in flowers.
Practical Tips
- Always use a microscope when examining flower powders to ensure accuracy.
- Keep detailed records of your findings, as misidentification can lead to incorrect medicinal uses.
- Use reference materials like the plates provided for comparison and identification.
Warnings & Risks
- Misidentifying pollen or stigma structures can result in dangerous misapplications in medicine.
- Incorrect examination techniques may lead to false conclusions about plant species.
- Contamination from adulterants, such as daisies, can be difficult to detect without microscopic analysis.
Modern Application
While the techniques described in this chapter are rooted in historical practices, they still hold value for modern survival preparedness. Understanding pollen and stigma structures is crucial for identifying medicinal plants accurately. Modern advancements in microscopy have improved precision but the fundamental principles remain relevant. This knowledge can help in field identification of plants during emergencies or when resources are limited.
Frequently Asked Questions
Q: How can one distinguish between different types of pollen grains?
Different types of pollen grains can be distinguished by their size, shape, and the presence of spines. For example, clove pollen grains are the smallest with a six-sided, angled cavity, while Spanish saffron pollen grains are spherical and granular.
Q: What is the significance of examining the papillae of the stigma in flower identification?
Examining the papillae of the stigma helps in distinguishing between different types of flowers. For instance, the papillae of saffron are long and tubular with a blunt rounded apex, while those of American saffron are short and tubular.
Q: How can one identify adulterants in insect flower powders?
Adulterants like daisies can be identified by examining the structure of the achene. The epidermal tissue of the achene in daisies consists of palisade cells with thick white walls and no cavity, which swell perceptibly when placed in water.