48 DIMORPHIC BRANCHES IN TROPICAL CROP PLANTS. 



experiment, this field still appeared very distinctly superior to any 

 of the adjoining areas. 



Although no observations or tests were made to determine the 

 resistance of these plants tq disease, it is apparent even from this 

 single experiment that commercial crops of bananas can be produced 

 under conditions that would give a considerable measure of protec- 

 tion against disease. The resting tubers would be much less likely 

 to convey diseases than the sword suckers, and could be much more 

 easily disinfected. Some of the banana diseases that become ver}^ 

 serious in old plantations appear to have little or no effect upon 

 vigorous young plantations under favorable conditions. The more 

 frequent replanting of bananas, every two or three years, is being 

 advocated among the Jamaica planters, because the old stocks are 

 thought to " run out " and become less vigorous, and also because the 

 young plants can be brought into fruit with greater regularity." 



The possibility of producing a full and regular crop of large 

 clusters of fruit by the use of tubers instead of sword suckers would 

 also make it more feasible to use bananas in a rotation of crops, a 

 policy which may prove to be as desirable in tropical cultures as in 

 those of temperate regions, if a permanent use of the land is to be 

 maintained. If the destructive policy of raising bananas for a few 

 years and then abandoning the land continues to be followed in 

 Central America, it will probably not require many decades to ex- 

 haust all the districts that are well suited to banana culture and at 

 the same time readily accessible from the United States. In a few 

 favored' spots where soil conditions are ideal or where new soil con- 

 tinues to be deposited by floods of adjacent rivers, permanent cul- 

 tures may be maintained, but in most places the prosperity of a 

 banana plantation appears to have definite natural limits. 



COMPARISONS OF DIFFERENT SYSTEMS AND TYPES OF BRANCHES. 



One reason why dimorphism of branches has not received more 

 attention is doubtless to be found in the fact that current botanical 

 classifications of buds and branches do not provide adequate recogni- 

 tion for the different kinds of diversity shown by the branches, as 

 among these tropical crop plants. The view generally stated or 

 implied in text-books is that branches are to be divided, with refer- 

 ence to their methods of origin, into two principal kinds, axillary 



» " There is a growing tendency throughout the whole island to reduce the 

 period of ratooning and to replant-every two or three years, as it is found that 

 by so doing the crops may be better limed for the American market, as after 

 first ratoons the plants fruit somewhat irregularly." (See Stockdale, F. A., 

 " The Question of a Banana Industry," Journal of the Board of Agriculture of 

 British Guiana, vol. 3, no. 2, 1909, p. 81.) 

 198 



