488 



SPECIAL PLANT PATHOLOGY 



?C^^ 



division, and by a sort of gemmation. The myxamoeba are provided 

 with several nuclei. The formation of spores soon begins by the suc- 

 cessive simultaneous divisions of the myxamoeba, so that each nucleus 

 and surrounding mass of cytoplasm is differentiated, as a spore by the 

 formation of a spore wall about them. The diseased ceUs are crammed 



full of such spores, which escape 

 only when the root disintegrates. 

 The liberated spores will germi- 

 nate in water in from four to 

 twenty-four hours and later the 

 parasite gains entrance to the 

 roots of the cabbage plant. The 

 organism causes an excessive 

 formation of new cells so that a 

 gall, or canker results. 



In order to check the organ- 

 isms, soils have been treated with 

 lime, sulphur and other fungi- 

 cides. Liming, using two tons of 

 quicklime to the acre eighteen 

 months before planting, has been 

 found the most reliable with the 

 destruction of the refuse of pre- 

 vious crops by burning. 



Carnation (Dianthus 

 caryophyllus, L.) 



Alterniose {Alternaria 



Fig. 169. — Cabbage roots showing club- 

 root caused by a parasitic slime mould, 

 Plasmodiophora brassioB. (From Marshall, diawiAJ, Stev. & Hall). Through 



Woronln)'"' "^"""'^ "'""'"' "' ^°^' "^'"^ Connecticut, Pennsylvania, Dis- 

 trict of Columbia and North 

 Carolina this disease of the cultivated carnation has been recently quite 

 troublesome. The leaves and stems, especially at the nodes, are dis- 

 colored with spots of ashen whiteness with a central black fungous 

 growth. The spot is dry, shrunken and thinner than the surrounding 

 healthy parts of the leaf, and is either circular, or somewhat elongated 

 in line with the long axis of the leaf. The nodal spots involve the leaf 



