78 LON A. HAWKINS 



these experiments were similar to those of the previous series, with some 

 differences due to the lower concentration of the lead salt. Practically no 

 appressoria were formed with the combination containing the o.o5m con- 

 centration of Ca(NO 3 ) 2 , germination being here (see fig. 5) about the 

 same as that which occurred with the o.oooo2m concentration of the lead 

 salt alone. With a combination containing o.oim Ca(NO 3 ) 2 , the same 

 effect was obtained as with 0.00004111 Pb(NO 3 ) 2 alone, and with combina- 

 tion containing o.oo2m Ca(NO 3 ) 2 about the same effect was evident as 

 with a concentration of o.oooo5m Pb(NO 3 ) 2 alone. In the combinations 

 with o.ooim and 0.0005111 Ca(NO 3 ) 2 the results were practically the same 

 as with a concentration of o.oooim Pb(NO 3 ) 2 alone; most of the germina- 

 tion here gave appressoria. 



With a o.oooi6m concentration of Pb(NO 3 ) 2 in combination with the 

 same concentrations of Ca(NO 3 ) 2 as were employed in the two series 



Fig. 5. Germinating spores from combination 

 solution containing 0.00033111 Pb(NO 3 ) 2 and 0.05111 

 Ca(NO 3 ) 2 X 650. 



above described, the concentration of the calcium salt in which the majority 

 of the germinating spores formed normal tubes (instead of swellings and 

 appressoria), and the concentration in which only an occasional spore 

 formed a normal germ-tube, were somewhat lower than in the previous 

 series, as was to be expected. The combination containing a o.oo2m con- 

 centration of Ca(NO 3 ) 2 gave practically the same effect as did the con- 

 centration of o.oooo/mi of the lead salt alone, while that containing a o.ooim 

 concentration of Ca(NO 3 ) 2 gave results similar to those obtained with a 

 o.oooo2m concentration of the lead salt alone. Combinations containing 

 Ca(NO 8 ) 2 in concentrations of o.O333m, 0,04111 and 0.05111, respectively, pro- 

 duced the same sort of germination as was obtained with a concentration 

 of 0.00033111 Pb(NO 3 ) 2 combined with a 0.05111 concentration of the calcium 

 salt ; germination was practically all normal, only an occasional appressorium 

 or swelling being found. 



From the above data the conclusion seems warranted that the same 

 molecular ratio of the calcium salt to that of lead produces practically 



