580 



SCIENCE. 



[N. S. Vol. XII. No. 303. 



sound ones remaining on the vines at the 

 close of the experiment. 



Treatment, sprayed 8 times 

 at 3 to 5 day intervals. 



Check 



10 per cent, mechanical 

 mixture kerosene and water. 



10 per cent, kerosene and 

 whale oil soap, 1 J lbs. to 1 gal. 



Whale oil soap, 11 lbs. to 1 



' Rose Leaf ' tobacco ex- 

 tract, 1 pt. to 1 gal 



' Rose Leaf ' as above and 

 kerosene 10 per cent 



' Rose Leaf ' as above, and 

 whale oil soap as above 



Check.* 



Check 



1366 



1417 



1495 



1309 



1467 



1355 



1518 

 1490 188 

 1241 1 177 



589 39 

 526 !42 



As seen from the above table the number 

 of rotted fruits varied from 12% to 27% in 

 the different plots, the highest being one of 

 the checks and the lowest also one of the 

 checks and the plot receiving ' Rose Leaf ' 

 and kerosene. The average for all the 

 plots was 20i%, for the three check plots it 

 was 17|%, for the three plots receiving 

 ' Rose Leaf tobacco extract either alone or 

 in combination, it was only 15|%, while for 

 the three whale oil soap plots it rose to 

 21f % . These figures slightly favor the to- 

 bacco treatment, but as the average is only 

 27% less than that of the checks and only 

 5% less than the average for all the plots, 

 while the different check plots varied among 

 themselves as much as 15%, it seems best 

 to consider the case as not proven. Thrips 

 were almost entirely absent from the to- 

 mato plants this year and no other small 

 insect was observed in suificient numbers 



* This plot was intended for Bordeaux mixture 

 and Paris green, but owing to accident to spray 

 pump, only one application was made and that is 

 not believed to have affected the result. 



to account for the spread of the disease. 

 It must be admitted that the problem of 

 how natural infections occur is still un- 

 solved, and that no remedy has been dis- 

 covered. It was noted that on some vines 

 nearly or quite all the fruits rotted, while 

 on others in the same plot all remained 

 sound. The high average in plots 1 and 3 

 was due to the condition of a few plants 

 where all the fruits became diseased and 

 plot 9 would have had a lower average than 

 any but for a few plants in the outside row. 

 It was also noted that dry weather favored 

 the spread of the disease, while a period of 

 daily showers would almost entirely pre- 

 vent the appearance of new cases. This 

 agrees with previous observations. 



The number of wormy fruits varied from 

 13% in plot 1 to 42% in plot 9. This pro- 

 gressive increase in numbers indicates that 

 in this case the position of the plot in the 

 field rather than the treatment was the 

 controlling factor. 



Concentric Spore Spots : By B. D. Halstbd. 



The spores of parasitic fungi generally 

 reach the surface of the host for aerial dis- 

 tribution by either the hyphse of the fungus 

 passing out through the stomata and after- 

 wards bearing the spores free in the air, or 

 in forming in masses just beneath the epi- 

 dermis through which they break and thus 

 become liberated. The peronosporas, cerco- 

 sporas, ramularias and macrosporiums are 

 good examples of the first named method, 

 while the cystopus and gloeosporium are 

 instances of the second type, which includes 

 the vast number of members of the true 

 rust fungi. In ^cidium and allied genera 

 there is a special organ which envelops the 

 spores, lifts the epidermis and bursts open 

 as a deeply-seated cup. Similar to this is a 

 large number of the fungi imperfecti with the 

 septoria-5 and phylostictas as types where 

 the pycnidium makes a way through the epi- 

 dermis and presents its mouth free for the 



