14 
eastward it is progressively worse, till it reaches a climax in Florida, 
which seems to possess the requisite soil, humidity, ami warmth for the 
proper euvironmeut of the Auguillula, aud consequently its complete 
development for mischief in gardens and groves. 
Add to this the cultivation of special food plants extremely suscept- 
ible to invasion by the worm, and there can be no wonder at its prodig- 
ious increase. 
TEMPERATURE. 
The question of temperature is no doubt one of great importance in 
determining the boundaries of this disease, perhaps more so than food- 
plants or soils. 
The soil that is annually frozen from 6 to 10 inches is nearly disin- 
fected from the worms, especially those existing in a free state in the 
soil, or inhabiting the soft roots of annual plants, and this may explain 
why southern Michigan, northeastern Ohio, and New Jersey,, with as 
sandy a soil as Florida or south Georgia, still escape the plague in the 
Peach orchards. 
The Chenopodium, Artemisia, etc., abound in these States, and no 
doubt are the habitat of Anguillulas, but the continued cold reduces 
their number to the minimum each year, and the fibrous-rooted trees 
are unharmed. 
Again, in some cold localities the trees kept in hot-houses are af- 
fected; those without in open ground escape. 
Places favored with hot, dry summers and cold, wet winters will not 
likely ever suffer from the ravages of the root knot. 
My experiments are conclusive that below 50° in fluid, and above 
that, dry, the worms are inactive, paralyzed by cold, and shriveled by 
dryness and heat, and the inference is plain that parties wishing best- 
results must either choose unsusceptible stocks, for grafting or budding 
trees liable to infection by the Auguillula, remove to favored loca- 
tions, or find some means of destroying the worms. 
The arid regions of the West fill one indication, the others are still 
subjudice, but in a fair way for determination. 
SOILS. 
It can not be questioned but that a light, sandy soil offers least re- 
sistance to the progress of the Auguillula after its liberation from de- 
caying roots either encysted or free. 
Experiments with air-dry soil show that water penetrates sand in half 
the time that it will penetrate clay, and over large areas of cultivated 
land the proportion would still be greater in favor of the sand. 
Loose soils, mixed with decaying vegetation and humus, offer still 
better facilities for irrigation, and this explains the fact that locations 
highly fertilized with composts, stable manure, or leaf-mold show the 
root-knot quicker in plants than compact or virgin soils, and the worst 
