145 



Edible Products. 



Under the head off* Varieties are discussed the thick-skinned forms grown in 

 Guatemala, and their introduction into Porto Rico bids fair to be; a distinct 

 advance. The improvement of the existing forms in this respect by hybridisa- 

 tion and selection is, as with all other characteristics, an untried field. The 

 chief drawback is, of course, the length of time that must elapse before the 

 young plants reach fruiting age. The tree can, however, be grown with little 

 care; and with the experiments carefully outlined, so that the desired results 

 may be kept in view, the trouble and expense would not be great, and in time 

 some really valuable results might be expected. 



UNIFORMITY,— With the avocado, as with other fruits, a regidar market 

 can only be expected when there is a regular supply of a uniform product. In 

 Porto Rico the fruit varies in form from almost spherical to those that have 

 a long, curved neck. The extremes probably represent distinct wild strains, 

 but the fruit seems to come true to seed to only a limited extent, and anything 

 like perfect uniformity can only be expected with asexually propagated plants. 

 Rolfs shows that the varieties in Florida do not come true to seed. 



Extension of Season.— Extension of season is an important desideratum, 

 especially in the direction of later fruiting forms, the desirability of which is con- 

 sidered farther on. Advance in this direction is likely to be made by the 

 introduction of new varieties and, perhaps, by extending the cultivation of the 

 trees to regions of more continuous moisture where the season of flowering 

 can be to some extent controlled. The tree flourishes in many localities where 

 it fails to bear fruit, and, as with the mango, this sterility is usually found in 

 localities of almost continuous humidity. Under such conditions an artificial 

 check, such as root pruning, has been found to induce flowering and the setting 

 of fruit. This can easily be overdone, however, in which case the trees will 

 bear one large crop and then die. Some of the most prolific trees are those 

 grown in small depressions of porous rock in Southern Florida, where the 

 plants are, in a manner, root bound, while the porous nature of the rock 

 affords good drainage. There are a number of ways in which the growth may be 

 checked and the yield increased. The baring of the roots to the sun would 

 appear a very satisfactory method. A custom of hacking the trees to make them 

 bear is practised by the Indians of Mexico. In any case where the fruiting is 

 induced by artificial means the season will be more or less under control. 



Seed Reduction.— In most forms of avocado the seed forms a consider- 

 able proportion of the bulk of the fruit, and its reduction is to be desired. 

 As pointed out by Rolfs, it is important that the seed should fill the cavity, 

 as otherwise the movement of the seed during shipment damages the pulp. 

 Modern discoveries in evolution and plant breeding make it evident that the 

 character of seedlessness in a fruit, though rarely secured, may be sought in 

 either of two ways : (1) If the plant is normally open fertilised, self -fertilisa- 

 tion and selection for a number of generations will in many cases produce 

 sterility, and consequently seedlessness. (2) By artificially pollinating the flowers 

 with pollen from a variety or species so far removed that the fertilisation is 

 imperfect, the exocarp or other parts of the fruit that are entirely the product 

 of the female parent may develop, while the seed, which is the result of the 

 union of the male and female elements, remains small or is aborted entirely. As the 

 avocado is open fertilised, the first method mentioned is perhaps more simple, but 

 will take more time, and this is, of course, a great disadvantage with fruits that 

 are so long in coming to bearing. 



The second method necessitates sufficient skill to effect hybridisation, and 

 this of the most difficult kind, but has the advantage of securing much quicker 



