58 MAINE AGRICULTUIL\L EXPERIMENT STATION. I915. 



that this black heart is not a disease in the sense that it is either 

 produced by fungi or bacteria. It is apparently a physical con- 

 dition arising from some factor or factors in the growth of the 

 plants, which laboratory studies failed to disclose. 



One of the objects of the demonstration experiment above 

 described was to obtain light upon the nature and cause of black 

 heart. The crops from these plots were all tested for black heart 

 by cutting 100 turnips taken at random from eadi plot. The 

 results of this examination are given in the three last columns 

 of the table on page 55. 



While very little was learned by the season's experience as to 

 the cause of black heart, several theories which have been 

 advanced have been explained. The fact that on some of the 

 plots the turnips were all black hearted while on others they 

 were nearly all perfect, proves that the trouble is not due to 

 seasonal conditions, nor is it due to the seed used. It also bears 

 out the statement of the plant pathologist that this is not a 

 definite disease, for if it were all of the turnips in one row 

 would hardly be perfect while those in the next row would be 

 all black hearted. In the case of two rows growing side by side 

 of different varieties one was all black hearted and the other 

 entirely free from black heart. 



The previous observations made by Mr. Washburn that he 

 is "certain it is not the fish that gives the black hearted product" 

 did not hold in 1914, for the plot manured with fish chum alone 

 had all of the turnips black-hearted. It is not due to the chum 

 alone, for the plot without chum (fertilized with tankage, 

 mirate of soda, acid rock and muriate) had 65 per cent of the 

 turnips black hearted. When grown on barn dressing alone 26 

 per cent were black hearted ; when grown on barn dressing 

 with the addition of chemicals 16 to 24 per cent were black 

 hearted, on the three different plots. 



Four plots, fertilized alike with stable manure plowed in and 

 an application of nitrate of soda, acid phosphate, tankage and 

 muriate, were planted with different varieties. Three varieties 

 of rutabagas — Carter's Imperial, Skiwing's Purple Top and 

 Golden Neckless — and a true turnip — White Egg — were grown. 

 The Golden Neckless had a smaller yield than the other varieties 

 but was entirely free from black heart. The crop from the 

 Carter's Imperial had 18 per cent black hearted turnips, that 



