. Nature and development of plants . llupon them and cause an excessive loss of water. The stomataof floating leaves, however, are upon the upper surface and theirstoppage with water is prevented by waxy coatings, as can beeasily demonstrated by dipping a leaf of a water lily or spatterdock in the water. When the leaf is removed the water runsoff of the waxed surface without wetting it. Some leaves aremore or less erect, as the cattails, rushes and grasses, and thesehave the stomata developed more or less evenly on both the intense light of midday is not beneficial to thesel
. Nature and development of plants . llupon them and cause an excessive loss of water. The stomataof floating leaves, however, are upon the upper surface and theirstoppage with water is prevented by waxy coatings, as can beeasily demonstrated by dipping a leaf of a water lily or spatterdock in the water. When the leaf is removed the water runsoff of the waxed surface without wetting it. Some leaves aremore or less erect, as the cattails, rushes and grasses, and thesehave the stomata developed more or less evenly on both the intense light of midday is not beneficial to theseleaves and the blade of the leaf is consequently placed parallelwith the suns rays. This arrangement of the leaf permits adirect illumination of the leaf only in the morning and afternoonwhen the intensity of the light is feebler. Leaves develop fewerstomata in a dry atmosphere and intense light than in moist andshady places. Light and moisture also influence the position ofthe stomata in another interesting way. Plants living in the. Fig. 24. Cross-section of a leaf of the inch plant, Tradcscantia, show-ing the delicate character of the cells and the raised stoma of this shade-loving plant. 34 U >CATI( >\ I IF ST( IMATA shade r in the presence of an abundant soil-moisture developthe stomata on a level with the leaf surface i Fig. 24), becausethere is no necessity of conserving the water supply. \-<<r thesame reason some aquatics have lost altogether the power olclosing their stomata. < ta the other hand plants that are ex]to arid conditions or drying winds develop the stomata wellbelow the surface of the leaf, as in the cactus and in the needlesof conifers (Fig. _m. s), or in furrows, as in certain gnor at the bottom of minute pores, as in the oleander. Thesedepressions remove the stomata from the dry wind- and prevenl the direct contact of the moist air in the leaf with the dry atmo-sphere. The pores in the oleander contain hairs which wouldcheck transpiration j
Size: 1894px × 1320px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublisher, booksubjectplants
