On the Cause of 6 Blindness ’ in Potato Tubers. 
BY 
ELIZABETH DALE 
( Sometime Pfeiffer Student, Girton College, Cambridge ). 
HE disease known as ‘ blindness’ in potato tubers is so called because 
A it more or less completely destroys the ‘ eyes so that tubers thus 
affected are worthless for use as ‘ seed In addition to the symptom of 
blindness the surface of the tubers becomes rough and dark brown on 
account of a large formation of cork. When such a tuber is placed in damp 
air it becomes covered with a fine white mycelium, belonging to Verticillium 
albo-atrum , which produces the characteristic small conidia. If a blind 
tuber is cut across, the disease is seen to be confined exclusively to the eyes 
and to a narrow zone immediately below the cortex, which is thickened by 
the cork formation mentioned above. In this zone there is the fine mycelium 
of Verticillium albo-atrum . The whole of the interior of the tuber remains 
sound. 
Amongst a number of tubers which had been stored for seed during the 
winter, by far the greater number were blind. Some of these were planted 
in pots in a cool greenhouse, and others in the open. A few rotted away, 
some remained sound but produced no shoots, others formed fresh eyes 
which developed into shoots. These at first appeared healthy, but later 
most of them showed signs of leaf-curl and leaf-roll, becoming yellow in 
colour, and gradually withering and drying from below upwards. In the 
leaves of the plants grown in the greenhouse a bacterial disease appeared 
which is considered in a separate paper . 1 No mycelium was in any case 
found in the subaerial parts of the plant, though one shoot was cut down 
and every internode and leaf microscopically examined by means of sections. 
The subterranean stems, especially those nearest to the old tuber, were 
covered with elongated brown patches due to Verticillium albo-atrum and 
exactly resembling the figures given by Reinke and Berthold . 2 These 
brown patches spread from the old tuber up the new shoots and along the 
underground stems which produce the new tubers, and so into these new 
1 Dale: A Bacterial Disease of Potato Leaves. Annals of Botany, vol. xxvi, No. ci, Jan. 1912, 
p. 134. 2 Reinke and Berthold: Zersetzung der Kartoffel, 1879. 
[Annals of Botany, Vol. XXVI. No. CI. January, 1912.] 
K 
