Transactions and Proceedings of the Botanical Society of Pennsylvania Volume 2, PT. 1

Transactions and Proceedings of the Botanical Society of Pennsylvania Volume 2, PT. 1

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ... showed comparatively little oscillation during the day; the highest temperature did not cause complete closure even when combined with the intense light. At II:30 A. M. the full light fell on the plant, but it remained fully expanded until the temperature passed the 90 F. mark, when it showed signs of paraheliotropic movement. The same behavior was recorded for several days in succession. Electric St1'muIations.--The stimulus was applied at a temperature of 80 F. The leaflet responded in 0.9 seconds and continued to fall for one minute. The shock killed the leaf and in half an hour it had completely wilted. Another rather younger leaf showed a latent period of 2.25 seconds at the same temperature. It also died from the shock. SUMMARY. 1. Light plays the most important part in the normal movements of the leaflets of the Oxalidaceae, heat and humidity being secondary. 2. The leaflets reach their highest points soon after sunrise, after which they sink again for a short time. The rest of the movements during the day depend on the conditions of their environment. 3. Leaflets in the dark do not cease movement until they have become degenerated. Generally this period is longer than Pfeffer has found for the plants he experimented with. Autonomous movements largely enter into the "dark" curve. 4. In blue light leaves generally oscillate less during the day than in white light, but in a week's time they become almost normal. 5. Heat from a heated wire, and ice, are poor stimulants. 6. The physiologic condition of the leaflet, as well as its previous history, has much to do in influencing its behavior. 7. Electric stimulations give the most uniform results, because they can be so accurately repeated. 8. A number of species assume their...show more

Product details

  • Paperback | 126 pages
  • 189 x 246 x 7mm | 240g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236744047
  • 9781236744043