4 oo POPULAR SCIENCE MONTHLY. 



In the last two decades of the last centurv, scientific effort concerned 

 itself chiefly with accumulating knowledge concerning fungi and in- 

 sects. Vast numbers of these were classified, catalogued and described. 

 In other words, the means of diagnosis were perfected and diseases 

 were grouped into natural classes according to their causal agents. 

 Attempts toward the development of methods of treatment by the 

 use of various sprays were more or less effective. Indeed, spraying had 

 been advocated to some slight extent for a century or more as a remedy 

 for insect and other plant diseases. The variety of spraying sub- 

 stances recommended ranged from clay, ashes and cow manure to 

 sulphur, lime, salt, etc. One writer recommended " The applying 

 around the base of the tree; flax, rubbish, sea weed, ashes, lime, sea 

 shells, sea sand, mortar, clay, tanner's bark, leather scraps, etc." — evi- 

 dently not a homeopathic prescription. The variety of substances 

 recommended raises suspicion that the efficiency of no formula was 

 demonstrated. In 1787 we find the heroic advice, 'just wet the trees 

 infested with lice, then rub flowers of sulphur upon the insects, and 

 it will cause them all to burst.' Some decided progress was, however, 

 made. As early as 1842, a whale soap was used and retained favor; 

 quassi, hellebore and tobacco were standard insecticides as early as 

 1855. Sulphur was used for the mildews and bluestone for wheat 

 smut. 



The last twenty years of the nineteenth century mark the beginning 

 of a new epoch in plant protection. For this there are three reasons: 

 first the increased aggressiveness of a certain fungous disease, the 

 grape mildew, in Europe; second, the rapid spread of the potato bug, 

 somewhat pedantically termed the Colorado beetle, and, third, resulting 

 from these two, revolutionary changes in materials and methods for 

 treating plant diseases, both fungous and insect, in the new world and 

 in the old. It is a matter not entirely without interest that the revolu- 

 tion in European methods may be definitely traced to typical Ameri- 

 can aggressiveness, inasmuch as the activity arousing fungus was of 

 American importation. 



In Europe the invasion of the downy mildew of the grape in 1878 

 was unchecked by the most vigorous fungicides then used. All are 

 familiar with the story of the great benefit conferred upon humanity 

 through the predatory habits of the French boys in the vineyards that 

 produce the famous Bordeaux wines. The rows lying nearest the 

 roadway were sprinkled with verdigris or a mixture of lime and blue- 

 stone, to give the impression that the fruit was poisoned. In 1882 

 Millardet, of the faculty of the sciences, noticed that the vines thus 

 treated held their leaves while others succumbed to the mildew. He 

 ascribed this effect to its proper cause, and conducted carefully sys- 

 tematized experiments, which resulted in giving to the world bouillie 



