20 
and no instances of healthy plantings on this soil type. The expe- 
rience of planters on the Florida Keys shows clearly that pineapples 
will grow in a calcareous soil providing it contains a very large amount 
of humus. This exception will be considered further on. 
POT EXPERIMENTS WITH DIFFERENT TYPES OF SOIL. 
The soil surveys having shown the calcareous nature of the Porto 
Rico soils unsuited for pineapples, it was desirable to see whether soils 
growing healthy plants would be rendered incapable of producing 
normal plants by the addition of calcium carbonate. For this pur- 
pose a series of pot experiments were carried out. 
Previous to this, however, certain preliminary experiments were 
made to show whether or not the trouble was to be attributed to the 
character of the soil, and also to explain certain apparent exceptions 
that occurred in the field. These experiments are here given in brief. 
On Mr. Noble’s plantation (see p. 8) some isolated patches of green 
plants were observed in the midst of chlorotic areas. It was desira- 
ble to see whether these patches of plants remained green due to 
differences in the soil or to individual variations in the plants them- 
selves. Soil from such a patch of green plants together with the 
plants themselves were shipped to the station, also the soil and plants 
from a chlorotic area. The soil from the green plants is No. 102, 
that from the chlorotic plants is No. 101 (see p. 10). These soils 
were placed in pots holding 8 pounds of moisture-free soil and were 
fertilized abundantly from time to time. Five chlorotic plants were 
placed in soil No. 101 and 5 in No. 102. Five of the green plants 
were placed in soil No. 101 and 5 in No. 102. Ten chlorotic plants 
were placed in a good garden soil free from calcitumcarbonate. The 
green plants in both soils 101 and 102 remained green for some time, 
but as their growth increased they later became chlorotic. The 
chlorosis appeared as rapidly in soil 101 as in soil 102. All the 
chlorotic plants placed in soils 101 and 102 remained chlorotic and 
grew but little. The chlorotic plants placed in the garden soil soon 
recovered their green color and made a good growth. Half of these 
recovered plants were then again returned to soils 101 and 102 and 
here they again became chlorotic and growth ceased. 
It is apparent from this that soils 101 and 102 are practically the 
same, and that the occurrence of green plants on one of them was due 
to the fact that the slips planted there were of greater vigor than the 
others. Field results confirmed this view, as later the isolated green 
plants on this plantation lost their color. The fact that chlorotic 
plants recovered in the good garden soil and again became chlorotic 
on returning to the original soil shows that the chlorosis was proba- 
bly induced by the soil and is not an organic disease. 
The following experiments and the success of the transplanted 
plants on Mr. Noble’s plantation (see p. 8) confirm this. 
(Bull. 11] 
