Page:Report of the Puerto Rico Experiment Station (IA CAT31294391015).pdf/10

 and chloropicrin fumigation in controlling this disease. Growth data obtained from the experimental plots prior to transplanting seedlings to nursery beds showed that plants grown in pure sphagnum moss suffered from nutrient deficiencies. Some plants in this treatment grew fairly well, but most appeared stunted. With an average height of 3.67 cm., plants in these plots were larger than those grown in untreated soil. Plants in plots of untreated soil plus 1 inch of sphagnum grew uniformly well, but not as vigorously as those in plots of treated soil plus 1 inch of sphagnum. Plants in the latter treatment averaged 7.83 cm., which made the largest growth of all treatments. Plants in treated soil, alone, averaged only 4.03 cm. in height. The results of this experiment indicate that both chloropicrin treatment and covering the soil with sphagnum were beneficial in controlling damping-off.

H. F. Winters and A. J. Loustalot

A field planting was made in November 1947 of Cinchona seedlings taken from a nursery experiment where they were grown with four levels of light and three levels of nitrogen. The experiment was continued in the field with three levels of nitrogen, in factorial arrangement with the previous three levels maintained in the nursery. One year after the plants were transplanted to the field a count of survival showed that an average of 12 plants, out of an original 15 per plot, survived. Variation between plots was slight. It was apparent that survival was not affected either by the nitrogen level maintained in the nursery or that applied to the plants in the field.

A. J. Loustalot and H. F. Winters

Cinchona seeds are planted in covered beds, and the plants are transplanted to shaded nursery beds when of sufficient size. Adjusting the plants to full sunlight is an extremely important phase of nursery management. An experiment was started in December 1947 to study the effect of light on the growth of Cinchona seedlings. The growth data obtained after 7 months of treatment showed that on the average the plants grown in reduced light were smaller and had less fresh and dry weight than did plants grown under the higher light level. This was true for both the C. ledgeriana and C. succrubra. Plants of the latter species were larger than those of C. ledgeriana, as would be expected.

The results of this study have practical applications in nursery work. At the time small Cinchona seedlings are transplanted from the seedbed to the nursery, it is necessary to protect them from wilt ing and direct sun by rather heavy shade. If the shading material is not partially removed as soon as the plants have recovered from transplanting, an unfavorable light condition is obtained, similar to that of this experiment. A high shoot-root ratio was obtained under condition of reduced light, which indicates that the rate of carbohydrate synthesis was probably very low because light was the limiting factor.

A. J. Loustalot. C. Pagán, and H. F. Winters

An experiment was initiated in June 1946 to study the relationship between size, age, and parts of young Cinchona trees and their total