308 Retort of the Assistant Horticulturist of the 
some sort, possibly to some mould, to prevent the penetration of which 
the tuber has developed a cork plate." 
The scab is one of those phenomena concerning whose nature and 
cause ^the most diverse opinions prevail. 
Several microscopical examinations of scabby tubers in various 
stages of the scab were made at this Station by Dr. J. C. Arthur, with- 
out detecting the presence of any fungus. I have been unable to find 
any reliable data indicating that the scab is caused by any known 
fungus. No remedy has been found that proves entirely successful in 
preventing the disease. The following experiments were attempted 
with a view of accumulating data to determine the cause and secure a 
remedy. 
Influence or Soil. 
In order to determine the influence of different kinds of soil in pro- 
ducing scab, medium-sized tubers that were smooth (or free from 
scab) were planted in eight-inch pots containing different soils, and 
placed in the greenhouse February 17. Four kinds of soil were used, 
two pots of each, muck, sand, garden soil and clay. After planting, all 
were treated as nearly alike as possible. The products of the tubers 
were removed from the pots May 31, after the tops were all dead, and 
carefully examined for scab. The per cent of scabby tubers and also 
the degree of scab were as follows: 
Wholo No. Per cent Degree 
of tubers. scabby. of scab. 
Muck 13 62 1 
Sand 3 100 2 
Garden soil 8 100 3 
Clay 3 100 4 
The muck proved the least favorable to the production of the scab. 
It was the only soil that produced any tubers entirely free from scab. 
The scabby tubers were affected in a less degree than those grown in 
the other soils. All the tubers grown in the other soils were more or 
less scabby, thos£ grown in sand ranked next in degree of scabbiness, 
those in clay were the most affected. It is not safe to generalize from 
an experiment on so limited a scale, yet the result tends to show that 
soils of a loose, porous character produce tubers less affected by scab 
than those of a heavy, tenacious nature. 
The Effects of Excessive Moist uke on the Pkoduction of Scab. 
On May 6, forty-five rows of potatoes, each row containing eight 
hills, were planted near the water-tank in the west garden in such a 
manner that four hills of each row could be irrigated and four remain 
