18,1 Lee: Mottled Leaf of Citrus Trees 91 
12 cases out of 28 trees, or 42.85 per cent. Sweet orange on 
calamondin stock developed 12 cases out of 93 trees, or 12.90 per 
cent, and of 70 trees propagated on mandarin orange stock only 
3, or 4.28 per cent, developed mottled leaf. 
Similar comparison with reference to other species shows high 
percentages of mottled leaf on pummelo stocks, lower ones on 
cabuyao and sour orange stocks, and but small percentages on 
calamondin and mandarin orange stocks. A table has been pre- 
pared, combining all the species upon a given stock, and is given 
here as it presents a more comprehensive summary of the re- 
lationship of stocks to mottled leaf. 
TABLE 6.—Summary of the influence of various citrus species as stocks 
upon the susceptibility of citrus trees to mottled leaf. 
Total Trees affected with 
Stock. trees. mottled leaf. 
Number.| Per cent, 
POMROIO os. cacasc ccaeainecseeen es 1145 695 60.80 
Cabuyao ei 8d i i shh he Be edb thane Sebi be oe sant 41 14 34.14 
Both Oaiites sa a eine te Ol Se Bes 95 23 24.21 
Cnlavnorita oes oS, ia too, eels h ce ickkew seated 298 34 11.4 
SUA Sr a ok a a 5 ke ckwess onsen sees ees 465 22 4.78 
The differences between the stocks were even more impressive 
in the nursery rows than they seem when summarized in tables. 
Moreover, the effect of mottled leaf on the growth of the trees 
was very striking. Trees of the Valencia orange or Oneco man- 
darin, for instance, made a very substantial growth on mandarin 
orange stock. The same varieties, of the same age, on pummelo 
stocks of the same age in adjoining rows, were much smaller at 
the time of the observation and lacked the vigorous appearance 
of the trees on the other stocks. The photographs, Plates 2 and 
3, show the comparative growth of trees upon pummelo and 
mandarin stocks. 
The effects of the pummelo stock in inducing mottled leaf 
were very noticeable. A row of trees budded upon this stock 
would be badly mottled and stunted; a tree would then occur on 
which the scion had not grown and the stock had developed in 
its place. Such a tree of the unbudded stock would be perfectly 
normal, with no trace of mottled leaf, and much greater in size 
than the budded trees upon the pummelo stock. Very commonly, 
also, a pummelo scion upon pummelo stock would develop entirely 
free of the disease and make a normal growth. This and the 
observation that the mandarin and other species mottled badly 
on pummelo, while the pummelo itself on pummelo seldom if 
