Plant Studies; An Elementary Botany

Plant Studies; An Elementary Botany

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ...a period of cold as a period of drouth, and perhaps they are more familiar in connection with the cold period than in connection with the drouth period. 136. Temporary reduction of surface.--While the habits above have to do with regular drouth periods, there are other habits by which a temporary reduction of surface may be secured. For instance, at the approach of a period of drouth, it is very easy to observe certain leaves rolling up in various ways. As a leaf becomes rolled up, it is evident that its exposed surface is reduced. The behavior of grass leaves, under such circumstances, is very easily noted. A comparison of the grass blades upon a well-watered lawn with those upon a dried-up lawn will show that in the former case the leaves are flat, and in the latter more or less rolled up. The same habit is also very easily observed in connection with the largerleaved mosses, which are very apt to encounter drouth periods. 137. Fixed light position.--In general, when leaves have reached maturity, they are unable to change their position in reference to light, having obtained what is known as a fixed light position. During the growth of the leaf, however, there may be changes in direction so that the fixed light position will depend upon the light direction during growth. The position finally attained is an expression of the attempt to secure sufficient, but not too much light (see 13). The most noteworthy fixed positions of leaves are those which have been developed in intense light. A very common position in such cases is the profile position, in which the leaf apex or margin is directed upwards, and the two surfaces are more freely exposed to the morning and evening rays--that is, the rays of low intensity--than to those of more

Product details

  • Paperback | 76 pages
  • 189 x 246 x 4mm | 154g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236632796
  • 9781236632791