. Botany for agricultural students . Botany. 348 THALLOPHYTES as the living content of the cells. Their presence in the leaf causes a blackening of the veins and a yellowing of the mesophyll. The disease may spread to the stem, where it clogs the vascular bundles and destroys tissues. Plants attacked lose their leaves and are dwarfed or killed. Potato Scab.'—There are a number of organisms which at- tack the Irish Potato and cause scabby areas and the decay of the tuber. Among this group of organisms pro- ducing scab there is one of the higher forms of Bacteria scientifically called Actinomyce
. Botany for agricultural students . Botany. 348 THALLOPHYTES as the living content of the cells. Their presence in the leaf causes a blackening of the veins and a yellowing of the mesophyll. The disease may spread to the stem, where it clogs the vascular bundles and destroys tissues. Plants attacked lose their leaves and are dwarfed or killed. Potato Scab.'—There are a number of organisms which at- tack the Irish Potato and cause scabby areas and the decay of the tuber. Among this group of organisms pro- ducing scab there is one of the higher forms of Bacteria scientifically called Actinomyces chromo- genus (Fig. 301). Among other bacterial diseases of the Irish Potato, Black- leg^ is of considerable im- portance, especially in the Southern States. Pear Blight.' — This dis- ease occurs on many fruit trees, but is more serious on Pears and Apples. It is often called Fire Blight or Blossom Blight. The Bacteria enter the young twigs, usually through the flowers, and attack the cambium and cortex. The tips of the twigs with their flowers and leaves soon wilt, and in a few weeks blacken and die. Sometimes when the attack is quite general, scarcely a flower tip of an infected tree escapes. This not only results in loss of fruit, but the tree is often so disabled that death results. Figure 302 shows a Pear twig severely " Potato Scab. Bulletin 184, Vermont Agr. Exp. Sta., 1914. 2 Potato Tuber Diseases. Farmer's Bulletin 5U, U. S. Dept. Agr., 1913. ' Fire Blight Disease in Nursery Stock. Bulletin 329, Cornell University Agr. Exp. Sta., Fig. 302. — Fire blight on the Pear. The tip of the branch is being killed by the Bacteria. After Whetzel & 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 original Martin, John N. (John Nathan), b. 1875. New York : John Wiley & Sons, Inc.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1919
