always injurious to mango flowers, as they wash away the pollen, 

 injure the stigma, and cause the pollen to remain damp, thereby im- 

 proving conditions for the growth of the anthracnose fungus which 

 is so destructive to the blossoms. The mechanical injury is easily 

 effected, for the one pollen-bearing stamen and the prominent pistil 

 are not protected by the small, widely divergent petals. The moisten- 

 ing of the pollen by the intermittent rains and low clouds, which 

 drift for some distance down the slopes of the highest hills of Porto 

 Rico, encourages the growth of the blossom-destroying fungus, and 

 this, together with the mechanical injury due to the heavy rainfall 

 in these sections during the mango blossoming season, is probably 

 responsible for the low yields and frequent fruit failures. 



The importance of moisture conditions should not be overlooked 

 in planting mangoes. Fortunately for the prospective orchardist the 

 rainfall in Porto Rico for corresponding months in different years 

 varies little, this constancy permitting the selection of a locality 

 where the mango blossoms during a season of light rainfall. Where 

 irrigation water is obtainable, a dry section would prove most satis- 

 factory as the blossoms would set fruit regularly and the fruiting 

 tendency could be encouraged by the proper application of water. 



The effect of wind on mango blossoms is also probably important, 

 although seldom referred to. Its stimulating effect may induce blos- 

 soming and its drying effect no doubt enables this fruit to set. For 

 a number of consecutive seasons it has been noted at Mayaguez that 

 trees situated in exposed places always bear more heavily on the 

 branches facing the prevailing winds, often producing a large per- 

 centage of their crop on the windward side. The drying action of 

 the wind probably protects the blossoms from fungus attack, since 

 the windward side of the tree is dry much earlier in the morning 

 than the leeward side or than trees in low, wooded, or otherwise pro- 

 tected places, where the heavy tropical dews remain on the leaves 

 until late in the forenoon. As the prevailing winds during February 

 and March, the principal mango blossoming season, are from the 

 northeast, the morning sun may be as necessary as the winds for 

 inducing blossoming, although the section of the tree facing the wind 

 is more prolific than that exposed directly to the morning sun, which 

 is south of east at this season. The stimulating effect of wind on 

 the growth of the branches is probably an important factor in the 

 production of blossoms, as the wood growth and inflorescence are 

 much heavier on the side of the tree facing the wind than on other 

 portions, sometimes causing a very one-sided development (PI. I, 

 fig. 1). This effect is more pronounced on imported varieties than 

 on uncultivated Porto Rican types and more so on some of the 

 imported varieties than on others. Those which afford the most 



