Plajit Diseases arid Bisects. 97 



that while the trees were planted a year previously and had 

 been dipped, according to custom there, in a caustic solution, 

 every tree examined by him bore a few specimens of the pur- 

 ple scale. The excitement on this subject in California has 

 been fostered by the claims of rival nurserymen engaged 

 either in the importation of Florida stock or dealing in varie- 

 ties grown at home, and from such contrary claims from per- 

 sons prejudiced by their business interests it is difficult to 

 extract the truth. A rigid quarantine, not absolutely prohibi- 

 tive were wisest, for great injustice might be worked by abso- 

 lutely prohibitive restrictions. Careful inspection and thor- 

 ough treatment, if they could be guaranteed, would prove an 

 effective safeguard, but it were unsafe to trust to them with- 

 out a rigid quarantine. 



"I have commenced a series of experiments upon the 

 black scale {Lecaniiim olecB), a species which, ordinarily 

 occurring upon the olive, has long damaged citrus fruits in 

 California. The horticulturist of the Wisconsin Station, 

 E. S. Goff, has modified the Nixon pump by adding a tube so 

 that kerosene may be drawn from one receptacle and a mix- 

 ture of soap and water from another, thus forming a mechan- 

 ical mixture in the act of spraymg. This modification, at the 

 request of Professor Henry, I have had tried in this series of 

 experiments, and although it is too early to state the results, 

 it may be said that so little time and labor are required in 

 preparing a stable emulsion that this mechanical substitute 

 will probably not come into general use. In this connection 

 it may be observed that the formulae recommended by some 

 of our most voluminous writers are very misleading, and are 

 calculated to produce only a mechanical mixture more or less 

 unstable. The use of kerosene temporarily combined with 

 water or soapsuds by mechanical means dates from many 

 years back ; it was a favorite remedy of my friend Thomas 

 Meehan, who urged it in 1871 in the Gardener's Monthly; 

 it was experimented with b}^ others, and I used it successfully 

 in 1872 against an undescribed lecanium on Austrian pine, 

 as also against aphides on the place of Julius Pitman, of St. 

 Louis, and in 1874 ^^^^ 1875 against the congregated young 

 of the Rocky Mountain locust. But the true and stable kero- 

 sene emulsion, which now forms one of the most satisfactory 

 and widely used insecticides, and which requires two parts of 



