. Lessons in botany. Botany. HOW PLANTS OBTAIN FOOD. 9' excreted by the cells of the gland, which glistening in the sun- light reminds one of drops of dew. For this reason the plant is called the sundew. When an insect alights on a leaf the viscid substance clings to it and holds it firmly so that it cannot escape. The glandular hairs then begin slowly to curve inward toward the centre of the 'leaf as shown in figure 68. Finally the margins of the leaf become inrolled also, so that the insect is held fast and close to the upper surface of the leaf. , Excretions from the leaf surface act as a d
. Lessons in botany. Botany. HOW PLANTS OBTAIN FOOD. 9' excreted by the cells of the gland, which glistening in the sun- light reminds one of drops of dew. For this reason the plant is called the sundew. When an insect alights on a leaf the viscid substance clings to it and holds it firmly so that it cannot escape. The glandular hairs then begin slowly to curve inward toward the centre of the 'leaf as shown in figure 68. Finally the margins of the leaf become inrolled also, so that the insect is held fast and close to the upper surface of the leaf. , Excretions from the leaf surface act as a digestive ferment upon the insect. 162. Nutrition of bacteria.—Bacteria are very minute plants, in the form, of short rods, which are either straight or spiral, while some are minute spheres. They are widely distributed; some cause dis- eases of plants- and animals, others cause decay of organic matter, while still others play an important role in con- verting certain nitrogen com- pounds into an available form for plant food. They absorb their food through, the sur- face of their body. They may be obtained in abund- ^h™dn*3d ance for study in infusions lobes' of plants or of meats. To demonstrate bacteria in infusions take a small quantity of hay or of meat. Place it in water and heat at about 60° C. for an hour. Then set the vessel containing the infusion aside in a warm room for several days., Numbers of bacteria will be developed, some of them probably motile. With a good micro- scope they may be demonstrated by mounting a drop of the infusion on a glass slip and preparingfor examination with the Fig. 67. Leaf of Venus fly- trap (Dionaea musci- Fig. 68. Leaf of Drosera ro- tundifolia, some of the glandular hairs fold- ing inward as a result of a 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 resemble the
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