Webber: The Improvement of Root-Stocks 
mean anything or is it purely acciden- 
tal? All of these trees are ordinarily 
sold and planted. Probably these dif- 
ferences in size are due to the same or 
similar causes as those responsible for 
the differences in size in bearing or- 
chard trees. 
A nursery grown at the Citrus Ex- 
periment Station for experimental pur- 
poses was planned with the idea of 
producing as uniform trees as possible. 
The sweet seedling stock used was thus 
selected when it was planted in the 
nursery, many of the small trees being 
discarded. Through the kindness of 
Mr. Shamel, the buds used for propa- 
gation were taken from record trees of 
standard type in order to further in- 
sure uniformity. Valencia and Wash- 
ington Navel oranges, Marsh Seedless 
grape fruit and Eureka lemon were the 
varieties grown. When this nursery 
was two years old and ready for orchard 
planting the trees were found to show 
the same variations in size of buds that 
have been referred to as being univer- 
sally present in ordinary nurseries. 
Had buds been taken indiscriminately 
from ordinary trees this variation 
would have been passed by as normal. 
As it was, this fact lead to a test of the 
different sizes of trees to determine, if 
possible, whether these differences in a 
nursery were of any importance in 
growing an orchard. Eighteen large, 
eighteen small and eighteen interme- 
diate sized budded trees of each variety 
were selected and planted in compari- 
son rows in the variety orchard at the 
Citrus Experiment Station, Riverside, 
California. These trees were all dug 
“bare root’’ to see that the roots were 
normal and not injured or diseased. 
All trees used in the experiment were 
normal and thoroughly healthy so far 
as could be determined. They were 
planted in the orchard in June, 1917. 
The severe heat coupled with ‘‘bare 
root” planting injured so many of the 
Eureka lemons that this variety was 
eliminated from the experiment. The 
Navels, Valencias and Marsh Seedless 
grapefruit stood the transplanting very 
well. 
293 
These trees have now been in the 
orchard three years and are five year 
old buds. They still retain the same 
comparative difference in size just as 
markedly as when they were transferred 
from the nursery. The large trees re- 
tain their lead and are still large. 
The intermediate are still intermediate 
in size and the small are still small. 
After two years in the orchard the 
small trees were about the same average 
diameter that the intermediate trees 
had when they were transplanted and 
the intermediate sized trees after two 
years in the orchard were about the 
same average diameter as the large 
trees when they were transplanted. 
Each grade is thus about two years be- 
hind the other in development. (Com- 
pare Frontispiece and Figs. 1 and 2.) 
To get some indication of the com- 
parative average size of the tops of the 
different groups, the top diameter of 
each tree was measured east and west, 
north and south and the height from 
the lowest branch to the top of the 
foliage. These measurements for each 
tree were multiplied together to give 
the volume of the cube that would en- 
close the top. The averages of these 
figures for each group in each variety 
are given in the following table. 
Average Comparative Size (in cubic inches) of 
Tree Tops, as Indicated by Product of East and 
West Diameter x North and South Diameter x 
Height from First Branch to Top. 
Large Intermediate Small 
Navelsienemonde: 204,04 20,185 12,541 
Maléneras saan 29,003 15,606 12,953 
Grapefruit........26,343 15,827 10,642 
While admittedly such figures are 
not exact measures of the top volume, 
they are believed to represent fairly 
accurately the comparative sizes of the 
trees in each group. 
FACTORS CAUSING VARIATION 
To what factors could this variation 
be due and is it of any importance in 
citrus propagation? A difference in 
the soil or in the nutrition available 
might cause variation in size but this 
cannot be the main cause of the varia- 
