. Agricultural botany, theoretical and practical. Botany, Economic; Botany. 750 FUNGI More frequently, however, if the mould is allowed to remain unchecked and the weather is unfavourable to the growth of the hop plant, the patches, especially on the lower surface of the leaves and on the young hops, become covered with extremely small, dark, rusty-brown specks, and the white, dusty character of the spot gradually disappears. The time at which mould is first observed varies with the season. Gardens once seriously attacked and neglected are always specially liable to an annual recurrence of the
. Agricultural botany, theoretical and practical. Botany, Economic; Botany. 750 FUNGI More frequently, however, if the mould is allowed to remain unchecked and the weather is unfavourable to the growth of the hop plant, the patches, especially on the lower surface of the leaves and on the young hops, become covered with extremely small, dark, rusty-brown specks, and the white, dusty character of the spot gradually disappears. The time at which mould is first observed varies with the season. Gardens once seriously attacked and neglected are always specially liable to an annual recurrence of the disease, unless measures are taken to get rid of the trouble by methods described below. Cause.âThe disease is caused by the fungus Spharotheca Castagnei Lev., whose white mycelium forms a ^mould-s^oV on the surface of the hop- leaves. In the early stages of development the slender hyphae of the mycelium spread over the surface of the leaf and send down short haustoria or ⢠suckers ' into the epidermal cells. The haustoria serve to fix the parasite to its â B ^ « 1- J -J- .. host, and at the same Fig. 254.â.(4, Mycelium and erect conidiophores of'Hop- mould' (Spharotlieca Castagnei Lev.). (Enlarged 100 time theV absOrb from diameters). B Portion of mycelium m of same fungus with conidio- the hop-plant the phore {a) from the apex of which conidia (c) have been . abjointed ; c^ germinating conidium ; t germ-tube. (En- nUtTimCnt nCCeSSary larged about 400 diameters). for the growth of the fungus. Not long after the hyphse are established on a leaf, erect. 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 Percival, John, 1863-1949. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
