citrus scab: its cause and control. 21 
p anied by blossoms. Between these main flushes an occasional but 
irregular putting out of vegetative parts is observed. 
In young groves which have not come into bearing the vegetative 
growth is quite comparable with that occurring in bearing trees, the 
chief difference being in the number of flushes. Vigorous young 
trees which are being forced by fertilizers and cultivation are likely 
to put on five or six distinct flushes during the first year after setting, 
these decreasing in number until the tree begins bearing a fair crop 
of fruit. After that time there are usually only three main flushes 
during the year. 
Nursery trees, both budded and seedlings, are continually sending 
out successive vegetative growths from early spring until late fall, 
frequently making an extension of as much as 60 inches during the 
year. Rough lemons especially have emerging leaves present prac- 
tically throughout the entire growing season, while the sour orange 
is inclined to be more regular in its growths, the more vigorous plants 
putting on about 10 flushes. 
DISEASE AS INFLUENCED BY THE STOCK. 
There is a widespread popular impression that grapefruit growing 
on rough-lemon roots is more susceptible to scab than when the same 
variety is grown on sour-orange or grapefruit stock under the same 
environmental conditions — that the stock lessens the resistance of 
the scion to this disease. 
In general, scions on rough-lemon stock produce a much greater 
vegetative growth during the first few years than is the case with other 
popular root systems. Such being the case, trees on these roots have 
many more leaves and perhaps a greater number of fruits passing 
through the stages of growth susceptible to infection. Under these 
actual conditions there is a considerable increase in the chances for 
trees on rough-lemon roots to become infected even where resist- 
ance remains constant. If the stock exerts an appreciable influence 
on the inherent susceptibility to scab it should show up at least occa- 
sionally in inoculation experiments. 
A critical study of the results from inoculation experiments 
conducted during the past five years, coupled with the summary of 
general orchard observations made over the same period, indicate 
that there is no material difference in percentage or degree of in- 
fection that could reasonably be attributed to immunizing or sen- 
sitizing influences produced by the stock on the scion. 
ADAPTATION OF THE FUNGUS. 
That citrus scab will eventually be as serious on the round orange 
as it now is on grapefruit is the belief of a large number of practical 
horticulturists and a few pathologists {23), This opinion is based 
