206 SECTIONAL ADDRESSES. 



requirements of some particular district, in order tliat it may be capable 

 of commercial exploitation. In the one case the botanist reveals to the 

 commercial grower the secret which will give him success ; in the other 

 the commercial grower insists on the botanist providing him with the 

 type of plant he requires in order to make an enterprise successful. Two 

 somewhat different aspects of the relations between pure and applied 

 botany. A few examples of the latter type of problem are worthy of 

 bringing to your notice, as they relate to such important crops as pistachio 

 nuts, limes and bananas. 



Pistachio nuts are grown as a crop in California, and the problem facing 

 the plant breeder, if he is to satisfy the grower, is to produce varieties 

 bearing nuts which crack naturally. If varieties are produced, the nuts 

 of which have to be cracked by hand, they are of no value commercially, 

 however good the nuts may be in size or flavour, since the labour cost 

 involved in cracking by hand in the United States is prohibitive if the 

 nuts are to be sold at a profit ! 



Fortunately scientific research has now produced the desired article, 

 and those who delight in pistachio ices, &c., can rest assured that they 

 are coloured and flavoured by the genuine article and not by some synthetic 

 product. 



Limes, again, the staple industry of Dominica, present a curious and 

 difficult problem. The wither- tip disease has made it imperative to carry 

 out experiments with the object of producing races or varieties immune 

 to the disease. 



There seems, fortunately, good prospect of success attending these 

 efforts, so far, at any rate, as the production of an immune type is con- 

 cerned. Dominica, however, is very hiUy, and the lime bushes are grown 

 on such steep hillsides that hand-picking of the fruit would be very costly, 

 and in some cases well-nigh impossible. The lime of commerce, as 

 is well known, has the usefiil habit of shedding its fruit when ripe, 

 so that the Dominican peasant merely has to go and collect the fruit 

 under the trees or bushes. The problem before the plant-breeder 

 working on limes, therefore, is to produce a lime which not only is 

 immune to disease, but which will also shed its fruit when ripe. Unless 

 this second essential can be attained the new variety is of little or no 

 commercial value. 



The banana problem, connected with the attempt to produce a strain 

 immune to Panama disease, is also hampered by a somewhat similar 

 economic question. In this case it is necessary that the fruits should be 

 incurved, so that in each ' hand ' the apices of the bananas curve inwards 

 towards the stem. In this way the bunches can be easily handled without 

 injury to the fruit, and also there is the further practical advantage — 

 they take up the minimum of space on board ship — -two practical 

 points which make all the difference between success and failure in a 

 commercial enterprise — but matters which may baffle the ingenuity of 

 the botanist and geneticist for many a long day before a satisfactory 

 solution, i.e. the successful combining of the two desired characters, can 

 be attained. 



Dr. Walter T. Swingle, Principal Physiologist of the U.S. Department 

 of Agriculture, has been writing to me recently about the remarkable 



