. Annual report of the Cornell University Agricultural Experiment Station, Ithaca, Cornell University. Agricultural Experiment Station; Agriculture -- New York (State). -lO Bulletin 253. green stem. Growth of the tube continues by the absorption of sap and other food material from the vine. The fine thread-like tube branches and spreads out for a short distance on the inside. Cross-walls are now formed and the growth is known as mycelium. The mycelium is the vegetative or growing stage of the fungus and, although rarely seen, is the stage which does the great damage. The threads not only
. Annual report of the Cornell University Agricultural Experiment Station, Ithaca, Cornell University. Agricultural Experiment Station; Agriculture -- New York (State). -lO Bulletin 253. green stem. Growth of the tube continues by the absorption of sap and other food material from the vine. The fine thread-like tube branches and spreads out for a short distance on the inside. Cross-walls are now formed and the growth is known as mycelium. The mycelium is the vegetative or growing stage of the fungus and, although rarely seen, is the stage which does the great damage. The threads not only push between the cells of the grape and in that way absorb the sap which would normally flow from one cell to another, but also penetrate directly into the cell and take up food material there. When the mycelium has established itself on the inside and can no longer be prevented from grow-. FiG. 179—On the left, black-rot spots on the leaf (natural size); on the right, photomicrograph of a small portion of a single spot showing fruit bodies of the fungus. ing or be killed by means of a poisonous spray, infection is said to have taken place; the leaf or vine is infected. Incubation. The mycelial threads grow for a short distance in all directions from the point of infection; never as much as an inch and usually not more than J to J inch. This growth takes place rather slowly and there is no external evidence of it until 12 to 20 days after infection took place. This time is known as the period of incubation. At the end of this time the diseased area changes color and that part of the leaf becomes yellowish brown in color. (See Fig. 179).. 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 Cornell University. Agricultural Experiment Station. [Ithaca, N. Y. ?], 1900-1910. James B. Lyon, State printer)
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