The berries on badly diseased vines do not develop, but shrivel up or remain sour, and in some cases dry up entirely. In others, again, they acquire a mawkish taste, lose flavor and sweetness, and make only inferior or bad raisins. These many different characteristics of the plague depend evidently on the stage of infection. They do not follow each other in any certain succession, nor do they all appear on the same vine. Some vines show one face of the disease, other vines show another, and the observer must have been previously acquainted with the disease before he can readily recognize it. _Nature and Cause._--The cause of the vine plague is not known. No deadly fungus has so far been found on the vine, nor has any other deadly parasite been found on the diseased vines. In California the vine plague has been studied by N. B. Pierce, of the Agricultural Department at Washington. He suggested once that the disease was of bacterial nature, but has not proved his theory, his investigations not yet being finished. Mr. E. Dowlen has also been investigating this disease, and at one time thought it caused by a fungus, which, however, was proved later by Dr. H. W. Harkness to belong to the non-injurious kind. No insects of any kind prey on the vines in sufficient numbers to cause the serious symptoms of the vine plague.[7] Whatever may be the true cause of the vine plague, certain it is that it resembles in its advent and spreading such diseases in men as cholera, yellow fever or the Oriental plague. The vine plague appears to be especially promoted by warm, moist air and rain, but it is not confined to damp places, nor has it as yet been ascertained in what relation it stands to locality and climate. [7] The most interesting and correct account of the vine plague yet published is found in an essay on “The Mysterious Vine Disease,” by Newton B. Pierce, read before the State Horticultural Convention, at Los Angeles, March, 1890, and published in CALIFORNIA--A JOURNAL OF RURAL INDUSTRY, May 10, 1890; Vol. 3, No. 18. In California it first made its general appearance in Anaheim in Orange county, in the month of August, 1884, when vineyards of old Mission vines suddenly stopped growing, and the grapes failed to color and ripen, while many of the vines died the same year. The plague attacks in preference vines growing on poor, sandy or alkaline soil, or in vineyards underlaid with hardpan. The weak vines succumb the first of any. This is the reason why so many vineyardists doubt the existence of any particular disease, contributing the poor condition of the vineyard to anything else than the true cause.