548 JOUENAL OF THE EOYAL HOETICULTUEAL SOCIETY. 



Lyman J. Beiggs^ considered that tobacco roots were attacked by 

 Thielavia much more severely when the soil was alkaline through 

 the too liberal use of lime, ashes, or manures containing carbonate 

 of potash. He therefore recommended sulphate instead of carbonate 

 of potash, the avoidance of lime on diseased fields, and the use of 

 superphosphate or dissolved bone.f Sorauer,| in his study of the 

 attack on Cyclamen, concluded that the disease appeared mostly when 

 the pl^nt had been excessively manured, over- watered, and so on. 

 Peglion§ expressed a very similar opinion with regard to the attack 

 on tobacco. Galloway || considered that proper care in selecting soil, 

 avoiding too great an excess of humus, and in transplanting would 

 prevent the attack on violets. AderholdH carried our numerous 

 inoculation experiments from pure cultures with plants liable to attack 

 and found great difficulty in reproducing the disease in them, although 

 the material had been obtained from sources where the disease was 

 rife. 



On the other hand other authors have regarded the fungus as an 

 active parasite, and have described experiments where infection has 

 been freely obtained. 



Our own experiments corroborate Aderhold's. In 1908 pots of 

 ordinary soil, without artificial manures, were sown with sweet peas 

 in the greenhouse, half of them being inoculated with active material 

 of Thielavia, the remainder being not inoculated. The plants grew 

 and flowered well, alike those inoculated and those not. No disease j 

 occurred. 



In 1909 a series was prepared as follows: — 



Soil + 



Superphosphate and Potassium Sulphate. 

 Tending to be Acid 



Soil + 



Powdered Chalk and Potassium Carbonate. 

 Tending to be Alkaline 



Half the Pots inoculated 

 with Thielavia 



Half not inoculated 



Half the Pots inoculated 

 with Thielavia 



Half not inoculated 



No disease 



No disease 



No disease 



No disease 



Thus, again, attempts to reproduce the disease failed, and in this] 

 experiment at least the increased alkalinity of the soil failed to en-l 

 courage the attack — all the plants grew and flowered well. | 



In 1910 a series of pots was prepared as in 1908, half being inocu-| 

 lated, half not, with the fungus. After the plants h,ad grown aboutj 



* L. J. Briggs. "The Field Treatment of Tobacco Root-rot," U.S.A. Depl 

 Agr., Bur. PL Ind., Circ. 7 (1908). | 



t I.e., p. 8. j 



+ P. SoRAUER. " Ueber die Wurzelbraune der Cyclamen," Zeifschr. fm 

 Pflanzenkr., v. (1895), pp. 18-20. I 



§ V. Peglion. " Marciume radicale della piantane di tabacco causato dall^ 

 Thielavia basicola Zopf," At,ti B. Accad. Linrei. ser. 5, vi. (1897), pp. 52-56. j 



II B. T. Galloway. CommervUil Violet Culture, pp. 170-174. 



H R. Aderhold. " Impfversuche mit Tliirlnrid ba.^icola Zopf/' Arbeit. Kgl\ 

 OesutuL, Biol. Abf., iv. (1905), pp. 463-465. | 



