316 EXPERIMENT STATION RECORD. 



where there is an excess of lime. Probably no cuiiric hydroxid or other 

 copper salt is present in solution where the mixture is properly made. 

 The cux)ric hydrate in freshly made Bordeaux mixture is in the form of 

 precipitation membranes, probably of a colloid nature, containing large 

 quantities of imbibed water. Upon standing, especially if the mixture 

 is agitated occasionally, the precipitation membranes disappear and are 

 replaced by crystals of copper hydroxid. The crystals are often in 

 the form of sphterocrystals. The calcium sulphate is thrown down 

 in the form of amorphous granules which upon standing often appear 

 as twin crystals. 



The character of the cuticle of the plant, whether easily wetted or 

 not, and fineness of the spray are factors which influence the adherence 

 of the mixture. Upon the evaporation of the mixture the calcium sul- 

 phate crystallizes out, cementing the precipitates together and to the 

 leaf. The calcium hydroxid, by absorbing carbon dioxid from the air, 

 gradually changes to calcium carbonate, which being very difficultly 

 soluble aids in cementing the precii)itates to the leaf. The colloid pre- 

 cipitation membranes by drying also aid in fixing themselves to the 

 surface of the leaf. Through the adhesiveness and difficulty of solu- 

 tion of the cementing substances the great adhesiveness of Bordeaux 

 mixture is secured. 



The cui)ric hydroxid is not dissolved until the calcium hydroxid has 

 been changed into a carbonate through the action of rains, dew, and 

 moist air. Small auiounts may be dissolved by the carbon dioxid of 

 the air, ammonium carbonate, nitrate, and nitrite, together with sub- 

 stances absorbed from the cells of the host, or possibly by substances 

 secreted by the fungus. The action of copper upon the germination of 

 various fungus spores and upon algte as reported by various observers 

 IS given, in which it is shown that many of them are very susceptible 

 to extremely dilute solutions. The following suggestions are given 

 regarding the possible action of copper on fungi: 



"(1) The spores may he prevented from germinating by inhibitory action; (2) the 

 protoplasmic content of the spores may be killed outright in a short time before 

 germination has commenced ; (3) throngh negative chcmiotropic action of the cojiper 

 hydroxid the germ tube maybe prevented from entering the plant; (4) the germ 

 tube maj- be so vreakened l)y copper in solntion as to Ije nnaT)]e to enter the host 

 plant; (5) the germination tnbes may be prevented from growing or be killed only 

 upon contact with solid particles of copper or its compounds, or with the cuticle or 

 other parts of the host impregnated with copper; (6) the germ tube may be so 

 much injured soon after germination as to cease growing before attempting to effect 

 an entrance into the host plant, or may be killed outright soon after appearing; (7) 

 the effect of the copper contained in Bordeaux mixture may be exerted at a later 

 stage of development of the fungi ; (8) the presence of a thick coating of copjier 

 salts might impede the fruiting of a fungus already wathin the tissues of the host 

 plant." 



Report of the botanical department, J. 0. Arthur {Indiana 8ta. 

 R2}t. 1895, pp. 21-28). — Among the most important investigations car- 

 ried on during the year were pot experiments with fertilizers on 



