. Botany for agricultural students . Botany. POTATO BLIGHT (PHYTOPHTHORA INFESTANS) 359 A spray that is very commonly used is Bordeaux mixture.' The oospores Uve over winter and may perpetuate the disease from year to year. Portions of diseased plants containing oospores, when hauled out in manure or scattered about by the wind, may be a means of spreading the disease. In some forms of the Peronosporales as in Albugo or White Rust, which forms white blisters on the leaves and stem of the Radish and other plants of the Mustard family, both the sex organs and conidiospores are produced internall
. Botany for agricultural students . Botany. POTATO BLIGHT (PHYTOPHTHORA INFESTANS) 359 A spray that is very commonly used is Bordeaux mixture.' The oospores Uve over winter and may perpetuate the disease from year to year. Portions of diseased plants containing oospores, when hauled out in manure or scattered about by the wind, may be a means of spreading the disease. In some forms of the Peronosporales as in Albugo or White Rust, which forms white blisters on the leaves and stem of the Radish and other plants of the Mustard family, both the sex organs and conidiospores are produced internally. The hyphae form in clusters under the epidermis and form conidiospores in chains which push up the epider- mis, forming white blisters which finally rupture and allow the spores to escape. In this Fungus the conidiospore produces a number of zoospores. In this order Pythium is some- times included, species of which at- tack seedlings in greenhouses, causing the rapid wilting known as damping off, when moisture and warmth are abundant. Some species of Pythium live in the water like the Saproleg- niales in which order Pythium is often put, while other species live in the soil. In contrast to the Water Molds, the Downy Mildews are chiefly para- sitic, much less aquatic and, having introduced the conidia, they depend less upon water for dissemination. But like the Water Molds the presence of zoospores and the character of the re- productive organs suggest a relationship to the Green Fig. 310. —The lower epidermis of a Potato leaf showing the conidiophores of the Late Blight protruding through the stomata and bearing conidiospores at the tips of their branches. Many times enlarged. ' The preparation as most commonly made consists of 5 pounds of copper sulphate and 5 pounds of stone lime dissolved in 50 gallons of water. Potato Spraying Experiments in 1906. Bulletin 279, New York Agr. Exp. Sta. Cer- tain Potato Diseases and their Remedies. Bulletin 72, Vermont Agr. Exp.
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