44 



concentration the spores gerr.iinated with long tubes as in 

 the simultaneous controls in distilled water. 



Series including combinations of Pb(NC2)2 with 

 Ca(N03)2 were carried out at three different concentrations 

 of the lead salt, C.COOlom, O.C0033m, and O.CCG66n. IVith 

 a O.0C066ra concentration of Pb(N03)2 no concentration of 

 the calcium salt was found which entirely suppressed the 

 formation of appressoria, though with a concentration of 

 0.05m Ca(NC3)2 only an occasional appressorium was found. 

 This combination gave practically the same results as were 

 found with a 0.00004m concentration of Pb{N03)2 alone, i.e. 

 somewhat over 5C per cent of the germination was normal, 

 though a considerable number of swellings and appressoria 

 were formed. In the combination of the same concentration 

 of Pb(N03)2 (0.00066m) with Q.004m of the calcitm salt the 

 effect produced was similar to that found in cultures with 

 0.00005m solution of Pb(N02)2» only an occasional normal 

 tube was foiind, these probably constituting less than 1 per 

 cent of the total germination. '7ith concentrations of O.OGlm 

 0.C02m and 0.003m Ca(N03)2 combined with a C.00C66m solution 

 of the lead salt, practically no normal tubes v/ere produced, 

 germination taking the form of appressorium like bodies and 

 swellings. These concentrations correspond to solutions of 

 Pb(NC3)2 alone varying in concentration from C.COlm to 

 .OOGlm. 



In the second series of combinations of Pb(NC3)2 



