GENERAL APPEARANCE OF THE DISEASE. 



13 



Newton 1). Pierce, the piitholotri-^t in cliaitie of tiie Pucitic coast labo- 

 ratory of the Department, and probaMy by others, but so far as can 

 be determined it has not hitherto received careful investiiratiou. 



GENERAL APPEARANCE OF THE DISEASE. 



Several greenhouses where the disease was reportiMl to t»e [)nsent 

 were visited by the writer, who found the calhis rottini;- oil usually at 

 or just below the surface of the o^round, the disease sometimes extend- 

 ing- down into the eorm, sometimes upward into the leaves, and fre- 

 quently in both directions. Occasionally the disease seemc'd to start 

 in the edire of the leafstalk (tig. 1), in tlie flower stalk, or in some under- 

 ground part of the corm, thougii 

 as a rule it started at the lop of 

 the corm just above but near the 

 surface of the ground. It was 

 also noticed that the disease was 

 worse and spread more rapidly 

 in those houses where the callas 

 were grown in solid beds. 



^Vhen a diseased corm was cut 

 open it was found that there was a 

 distinct line lietween the healthy 

 and the diseased portion of the 

 corm (tig. 2). The hcnilthy pm-- 

 tion of the corm is tirm and nearly 

 white, while the diseased part has 

 a decidedly brown color and is soft 

 and watery. AVhen the disease 

 extends upward int(j the leaves it 

 is the edge of the petiole that 

 first })ecomes involved, the afi'ected 

 part becoming slimy, without im- 



mediatelv losing its green color. As the disease proo-resses it extends 

 inward toward the center of the petiole and interferes with the trans- 

 ference of material between the corm and the leaf, the edges of the 

 leaf becoming pale, then brown. Pale spots becoming brown then 

 appear in other parts of the leaf blade, and finally the whole leaf 

 becomes brown and dead. Frequenth' the disease develops so rap- 

 idh" that the leaf rots off' at the base and falls over before it has time 

 to lose its green color. When the disease has progressed far enough 

 to attack the flower stalk, the flower turns brown and the stalk, 

 without having lost its color and f requenth' without having decayed 

 upward more than a fraction of an inch, eventually falls over. When 

 the disease works downward through the corm it sooner or later 

 reaches the roots, which become soft and slimy within, while the epider- 



FiG. 1.— A slightly diseased calla plant. 



