INFLUENCE OF FOREIGN POLLEN ON THE DEVELOP- 

 MENT OF VANILLA FRUITS 

 t 



By T. B. McClelland 1 

 Horticulturist, Porto Rico Agricultural Experiment Station 



INTRODUCTION 



The Agricultural Experiment Station at Mayaguez, Porto Rico, has 

 been conducting experiments for a number of years with a view to the 

 establishment of vanilla growing on a commercial scale in Porto Rico. 

 Material representing many species of Vanilla has been obtained, and the 

 adaptation of these species to Porto Rican conditions is being studied. 

 The questions of pollination, fertilization, yield, and character of the 

 finished product have been given attention. The two types of economic 

 value are Vanilla planifolia, a plant having a slender pod of high 

 quality, and the " vanillon " type, which has a shorter, thicker pod greatly 

 inferior in quality and market value to the pod of V. planifolia, but 

 which possesses a marked advantage in the ease with which it may be 

 cured, since on ripening it does not split open if allowed to remain several 

 days beyond a certain point in ripening which is difficult to determine, 

 as the change in color is slight. 



Since the production of hybrids presented alluring possibilities, various 

 reciprocal crosses were made with a view to the development of valuable 

 strains. It soon appeared that these fruits of these hybrids were notice- 

 ably different from the others on the same vines. In order to study this 

 phenomenon, numerous additional crosses were subsequently made. 

 The data presented belo^v show an immediate influence of the foreign 

 pollen on the form of the fruits. 



Only a very small percentage of vanilla blossoms are pollinated by 

 natural means in Porto Rico. In a series of blossoms of V. planifolia 

 under observation by the writer at the Porto Rico Experiment Station 

 only 1.5 per cent of the blossoms were so pollinated. 



In hand pollination the usual method and by far the simplest is to use 

 the pollen of the same flower. Where pollen from another flower of the 

 same species has been appUed, no resultant change in the form of the 

 fruit produced has been observed. 



The typical well-developed fruit of V. planifolia from a close-fertilized 

 blossom is a long slender capsule tapering at the stem end but carrying 

 its fullness well down toward the blossom end. It contains thousands 

 of tiny, oily, black seeds. 



• The writer wishes to acknowledge his indebtedness to Dr. H. J. Webber, Dean of the Graduate School 

 of Tropical Agriculture, University of California, for suggestions. 



Journal of Agricultural Research, Vol. XVI, No. 9 



Washington. D. C. , ^ Mar. 3,1919. 



„ (245) Key No. B-15 



