. Elementary botany. Botany. PATH OF MOVEMENT. 53 is communication throughout tlie entire length of the stem. (The function of the sieve tubes is supposed to be that for the downward transportation of sub- stances elaborated in the leaves.) 106 If we section in like maimer the stem of the sunflower we shall see simi- lar bundles, but the number is greater tlian eight. In the garden balsam the number is froni four to in an ordinar}' stem Ty-\m!it diameter. Here we can see quite well the origin of the vascular bundle. Between the larger bundles we can see especially in free-hand sections of
. Elementary botany. Botany. PATH OF MOVEMENT. 53 is communication throughout tlie entire length of the stem. (The function of the sieve tubes is supposed to be that for the downward transportation of sub- stances elaborated in the leaves.) 106 If we section in like maimer the stem of the sunflower we shall see simi- lar bundles, but the number is greater tlian eight. In the garden balsam the number is froni four to in an ordinar}' stem Ty-\m!it diameter. Here we can see quite well the origin of the vascular bundle. Between the larger bundles we can see especially in free-hand sections of stems througli wliich a colored solution has been lifted by transpiration, .as in our former experi- ments, small groups of the minute cells in the cambial ring which are colored. These groups of cells which form strands running through the stem are pro- cainbium strands. The cells divide and increase just like the cambium cells, and the older ones thrown off on either side change, those toward the center of the stem to wood vessels and fibers, and those on the outer side to bast cells and sieve tubes. 107. Fibrovascular bundles in the Indian corn.—We should now make a thin transection of a portion of the center of the stem of Indian corn, in order to compare the structure of the bundle with that of the plants which Ave have just examined. In fig. 6o is repre- sented a fibrovascular bundle of tlie stem of the Indian corn. The large cells are those of the spiral and reticulated and annular vessels. This is the woody por- tion of the bundle or xjlem. Opposite this is the bast portion or phloem, marked by the lighter colored tissue at /. The larger of these cells are the sieve lubes, and intermingled with them are smaller cells with thin walls. Surrounding the entire bundle are small cells with thick walls. These are elongated and the taper- f ig. 6o. ing ends overlap. They are thus slender Transection of fibrovascular bundle of ' ,, -, , Indian corn. .i, toward periphery of an
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