. The origin of floral structures : through insect and other agencies. Plants; Flowers; Flowers. THE ORIGIN OF FLORAL APPENDAGES. 137 asserting that nature has produced them in order to keep ants oS ; for that line of reasoning' is pretty sure to land us in faulty teleological methods. What causes them is not at present known in all cases; though we may perceive that certain conditions, as growth in water, can bring about their disappearance, as Dr. Kerner remarked in the case of Polygonum amphibium, which only has them when growing on land. If, however, we ask, for example, why the Sweet-bria
. The origin of floral structures : through insect and other agencies. Plants; Flowers; Flowers. THE ORIGIN OF FLORAL APPENDAGES. 137 asserting that nature has produced them in order to keep ants oS ; for that line of reasoning' is pretty sure to land us in faulty teleological methods. What causes them is not at present known in all cases; though we may perceive that certain conditions, as growth in water, can bring about their disappearance, as Dr. Kerner remarked in the case of Polygonum amphibium, which only has them when growing on land. If, however, we ask, for example, why the Sweet-briar has them all over it, and why the Dog-rose has none, I do not know how to reply to the question as yet. We may notice certain coincidences, that hairy herbaceous plants are com- moner in dry situations and smooth ones in watery; just as root-hairs occur in a loose sandy soil and their absence is noticeable in a heavy one; but we do not know how these difEerent media actually bring about these changes, though we may feel assured that it is solely due to the environment. If we, thus, look elsewhere than in flowers for any analogous processes they are by no means wanting. For example, it is simply the mechanical iri'itation brought about by contact with a foreign body, probably aided by moisture and a lessened de- gree of light, that causes the epidermal cells of the aerial roots of the Ivy and Orchids (Fig. 42) to elon- gate into adhesive or clasp- ""^ j, ing hairs, so as to grasp the r,g cells of roots of body for support. This is J^'ei^'^^Sy'"'*'• *• ™'>'«"^«»-' (»«" only a form of the ordinary root-hairs which are immediately developed when the tip is in contact with a moist soil, and each hair grips and glues itself. 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 resembl
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Keywords: ., bookcentury1800, bookdecad, booksubjectflowers, booksubjectplants
