. Botany of the living plant. Botany; Plants. APPENDIX A 641 Pollination. Compare first the " thrum-eyed " type of flower. The parts are numerically the same as in the " pin-eyed " ; but the style carries the stigma only half-way up the corolla-tube, corresponding in level to the stamens of the " ; The stamens are inserted at the throat of the corolla, corresponding in level to the stigma of the " ; The effect of this " dimorphism " is to increase the probability of intercrossing as a consequence. Fig. 492. Primula vulgaris. I
. Botany of the living plant. Botany; Plants. APPENDIX A 641 Pollination. Compare first the " thrum-eyed " type of flower. The parts are numerically the same as in the " pin-eyed " ; but the style carries the stigma only half-way up the corolla-tube, corresponding in level to the stamens of the " ; The stamens are inserted at the throat of the corolla, corresponding in level to the stigma of the " ; The effect of this " dimorphism " is to increase the probability of intercrossing as a consequence. Fig. 492. Primula vulgaris. I. short-styled type of flower (thrum-eyed) in section. II. long- styled type (pin-eyed). III. pollen of short-styled. IV. of long-styled types. V. stigmatic papillae of short-styled. VI. of long-styled type. VII. floral diagram. of repeated visits from bees to the two types of flower, which are borne on different plants. The sticky pollen deposited on the proboscis of the bee from the " pin-eyed " type will correspond in level to the stigma of the " thrum- eyed," and the pollen of the latter to the stigma of the former. These are what have been called " legitimate " crosses, and they have been shown to be more prolific than the " illegitimate ' crosses, between parts of unequal length. But self-pollination is not precluded. The gamopetalous corolla is effective in excluding smaller insects, while bees are attracted by honey, colour, and scent. (d) TETRACYCLICAE. ORDER : PERSONATAE. This Order includes a large number of showy plants of temperate and tropical climates, with tetracyclic, gamopetalous flowers, having the general formula S. 5, P. (5), A. 5, G. (2). The ovary is superior, and bilocular, and the number of ovules borne on the axile placenta is usually 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
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