23 
the warts and give rise to tufts of erect, brown, branched, and multi- 
cellular fruiting branches or hyphe. On these the dusky, spindle- 
shaped spores are produced. The spores are borne in abundance hear 
the ends of the hyph, which often show numerous scars where spores 
have been detached. The spores are usually one-celled, but occasion- 
ally are two, and very rarely even three-celled. They are very minute, 
being only 8 to 9 by 24 to 4u (about ;4;5 inch long and 33455 inch wide). 
The hyphex are mostly 30 to 75 by 2 to 44. The spores germinate by 
pushing out a slender thread from the side. 
Conditions governing infection of the host plant by the parasite.—It has 
been found that this fungus is remarkably sensitive to weather condi- 
tions and can fruit abundantly and spread rapidly only where the air 
is moist. In Florida the disease often makes no perceptible progress 
for weeks during the dry spring, but if a few days of damp weather 
come on, it suddenly spreads and develops very rapidly. Groves in 
low, moist situations are more subject to scab than those on high 
and dry lands. The fact that the fungus depends so closely on moist 
weather for its proper development and spread doubtless explains its 
almost total absence from California, where the atmosphere is much 
drier during the growing season than it is in Florida. 
Another important condition governing infection is that the tissue 
must still be growing to be subject to the invasion of the parasite. The 
period of greatest danger to both leaves and fruits is when they are 
young and tender and growing rapidly. This explains why old lemon 
and sour orange fruits are not badly deformed when attacked by the 
fungus after the moist weather of summer sets in. 
Treatment.—During the spring and summer of 1894 extensive experi- 
ments were carried on by one of the writers to discover, if possible, 
means of preventing scab on the lemon. Owing to the irregular bloom- 
ing of the lemon, the prevention of the disease was found to be a diffi- 
cult undertaking. However, it was demonstrated that Bordeaux mix- 
ture and ammoniacal solution of copper carbonate, if properly applied, | 
are efficient. The former is very effective against the fungus, but is 
more or less injurious to the fruit and foliage of the lemon, while the 
latter is almost an absolute preventive of the disease and causes very 
little if any injury to the tree. 
It was found highly important that all infected fruits be removed 
from the tree and from the ground beneath before blooming begins. 
This measure is absolutely necessary to insure the success of any treat- 
ment, and is of itself a great aid in checking the disease. All sour 
orange trees or sprouts from sour stocks should also be removed from 
the vicinity of lemon trees, since they are even more subject to scab 
than the lemon, and because not only the fruit but also the leaves can 
Support a luxuriant growth of the fungus. 
The disease can be prevented, to some extent, by planting the trees 
on dry soil and in localities having little rainfall during and immedi- 
