. Essentials of botany. Botany; Botany. 178 ESSENTIALS OF BOTANY 211. Flowers with Stamens and Pistils Each of Two Lengths.— The flowers of bluets, partridge-berry, the prim- roses, and a few other common plants secure cross-pollina- tion by having essential organs of two forms (Fig. 134). Such flowers are said to be dimorphous (of two forms). In the short-styled flowers, II, the anthers are borne at the top of the corolla tube and the stigma stands about halfway up the tube. In the long-styled flowers, I, the stigma is at the top of the tube and the anthers are borne about halfway up. An inse
. Essentials of botany. Botany; Botany. 178 ESSENTIALS OF BOTANY 211. Flowers with Stamens and Pistils Each of Two Lengths.— The flowers of bluets, partridge-berry, the prim- roses, and a few other common plants secure cross-pollina- tion by having essential organs of two forms (Fig. 134). Such flowers are said to be dimorphous (of two forms). In the short-styled flowers, II, the anthers are borne at the top of the corolla tube and the stigma stands about halfway up the tube. In the long-styled flowers, I, the stigma is at the top of the tube and the anthers are borne about halfway up. An insect pressing its head into the throat of the corolla of II would become dusted with pollen, which would be brushed off on the stigma of a flower like I. On leav- ing a long-styled flower the bee's tongue would be dusted over with pollen, some of which would neces- sarily be rubbed off on the stigma of the next short-styled flower that was visited. Cross-pollination is insured since all the flowers on a plant are of one kind, either long- styled or short-styled, and since the pollen is of two sorts, — each kind sterile on the stigma of any flower of similar form to that from which it came. Trimorphous flowers, with long, medium, and short styles, are found in a species of loosestrife.^ 1 See Newell's Header in Botany, Part 11, pp. Fig. 134. Dimorphous Flowers of the Primrose. I, a long-styled flower; II, a short- styled Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Bergen, Joseph Y. (Joseph Young), 1851-1917. Boston, Ginn
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