S6 REPORT OF OFFICE OF EXPERIMENT STATIONS. 



tion and propagation of the better varieties of mangoes, more than 

 40 varieties having been introduced from various tropical countries. 

 Of these, 12 fruited this year, and the station shoulcl soon be in a 

 position to tell which varieties are best suited to Porto Eican condi- 

 tions. The pineapple industry is developing rapidly, and since the 

 bulletin on pineapples was issued in 1909 the question of shade and 

 legimiinous cover crops has been given definite consideration. Va- 

 riet}^ tests of pineapples are being made, and the station has 27 

 varieties under observation. Experiments have been begun on the 

 fumigation of pineapple slips before planting to rid them of mealy 

 bugs. The results thus far do not appear to warrant the practice 

 unless measures are taken to keep the plants clean after they have 

 been set in the field. 



The banana plantation has been moved to more suitable ground, 

 and of the large number of varieties, 25 have been selected for fur- 

 ther study. It is already apparent that there was a large duplica- 

 tion of varieties received under different names. The reduction of 

 these duplicates will prove of value to future investigators. 



Work is under way on the improvement of those crops of the 

 island that are known to the mass of the people. These include 

 yams, yautias, sweet potatoes, pigeon peas, beans, etc. A collection 

 of 25 varieties of yams has been made and they are being tested for 

 yield, quality, etc. Two varieties. Potato and Guinea, appear most 

 promising for cultivation in Porto Rico, as they yield heavih^ and 

 possess desirable culinary qualities. The work with vegetables is 

 being continued to determine the causes of rapid deterioration in 

 qualit}'. Some attention is being given to ornamental trees and 

 shrubs, and hardwood and nut-bearing trees. Thousands of trees 

 have been distributed through schools and planters, and the work 

 seems to be rapidly gaining in appreciation. 



The chemical department has made decided progress during the 

 year. A large amount of analytical work was completed and a 

 number of important lines of investigations were continued. These 

 include studies on soil disinfection, the availability of nitrogen and 

 phosphoric acid in the native bat guanos, the effect of strongly cal- 

 careous, soils on the growth and composition of plants, the action of 

 lime in inducing chlorosis of plants, and the effect of various ratios 

 of lime and magnesia on the growth of plants. The results obtained 

 in the disinfection of soils which have become unproductive through 

 the presence of organisms of various kinds indicate that a wider 

 range of experiments is necessary before definite conclusions can be 

 drawn. The study of the cause of chlorosis in pineapples has been 

 concluded and the results have been published. It was found that 

 the Cdndition for chlorosis was too much carbonate of lime in the 

 soil. Two or more per cent of calcium carbonate in soils was found 



