18 
tio as tlie distance from the surface. Reversing tbe process, putting the 
infected soil below, showed the roots affected soonest in the peas planted 
deepest, indicating hut little action in the worms outside of that pro- 
duced by the percolation of water. 
No. 22. Another series of pots were watered with muddy water from 
infected earth, and though the pots contained sterilized soil the roots 
of the peas were badly affected. Microscopic investigation of the per- 
colate showed both free and encysted Anguillulae. (Note 9.) 
No. 23. Pots with sterile soil had one transplanted infected peach 
seedling in each, and four cow-peas. 
The trees soon died, and very shortly afterward the peas showed the 
infection, those nearest the dead peach roots the most markedly. 
In a spot of new and non-infected ground several trees, Peach and Fig, 
were planted. The central tree was knotty-rooted and died in a few 
mouths ; the next year tbe roots of the nearest trees, 15 feet away, became 
knotty nearest the dead tree, and now, after the lapse of four years, 
the disease extends to the tips of the roots of all the Fig and Peach trees 
in a circle 120 feet distant each way from the original infected tree. 
In another case, in a nursery on high pine laud, clay subsoil and free 
from disease, a number of peach roots, badly knotted, were brought 
from a distance and heeled in for a week. The disease spread in all di- 
rections from this nucleus. 
Again, in another peach nursery was a spot of low, damp, black soil. 
There was no root-knot the first year it was planted in peaches ; the 
seedlings grew well. The second year, a few trees were found in this 
spot with enlarged roots and destroyed. The third year, hardly a tree 
escaped, the disease extending along the thickly set rows of seedlings 
upward and in all directions on to the higher land from the hollow spot 
first in fee ted. 
In another case, clean fibrous-rooted trees were heeled in a day or so 
and planted in non -infected ground. The next year proved the most of 
them diseased. 
These cases prove conclusively that in areas not infected the disease 
can be easily introduced (1) by planting infected trees; (2) by the use 
of composts of muck and weeds from infected soils ; (3) by the distribu- 
tive action of water and air, the water carrying particles of soil and 
worms downward from an infected elevation, or by dry soil, frag- 
ments of dry roots, desiccated free or encysted worms carried in the air 
during sand-storms, whirlwinds, or the heavy currents of air preceding 
storms that often blow " bare " acres of plowed land and overwhelm ad- 
jacent fields with the soil thus borne on the wind; (I) soil containing 
these worms I have no doubt has been carried on the feet of men and 
animals and deposited in healthy fields, forming the nucleus of a de- 
structive agency, mouths afterward made visible by its effects. 
Instances are not wanting that can not be explained except by some 
such theory of contagion and manner of travel. 
