62 



ANNUAL REPORT 1918 AND 1919 



few winters he can pull it through? It occurs to him to crush a leaf, and 

 immediately he detects a familiar aromatic odor. It is of the Mexican 

 race! Naturally he will plant it, for its chances of success are excellent 



The classification which we have been using in the United States 

 for the last few years seems in general to be quite satisfactory. It covers 

 the majority of the varieties now in cultivation. It does not, however, seem 

 to cover every one of them, and we have not yet carried it to a point where 

 we feel absolutely certain in every case that we have made a corrct 

 diagnosis. We must continue to study the matter until we have gone to 

 the bottom of it. This involves an investigation of the avocados of all 

 tropical America, a work which will require some years, but it is to be 

 hoped that it may be carried to a conclusion. It will be a decided advan- 

 tage if this important subject can be studied thoroughly while the avocado 

 industry is yet in its infancy. 



Mexico probably offers more material for this study than any other 

 country. It is a vastly better field than Guatemala, because of its larger 

 area and the abundance of all the known races. In Guatemala trees of 

 the West Indian and Mexican races are comparatively scarce, the Mexican 

 especially. 



This subject must be studied first from a botanical standpoint, later 

 from the horticultural point of view. We must first know with what species 

 we are dealing, before we will be able to classify our horticultural races. 

 The differences between a botanical species and a horticultural race or 

 group are technical in character, and I will not here discuss them in detail ; 

 suffice it to say that the botanical species is the broader division, the horti- 

 cultural races occurring within the species. The question which is now 

 confronting students of avocado culture is this: Are the varieties with 

 which we are dealing nothing more than horticultural forms of a single 

 botemical species, or are there several different species involved? In the 

 past, we have generally considered that all of the cultivated avocados be- 

 longed to the species Persea americarta of Miller, formerly known as Persea 

 graiissima of Gaertner; but it seems highly probable that we have held to 

 this belief simply because the avocados have never been studied sufficiently 

 to bring to light the specific differences which separate some of the groups 

 we have termed horticultural races. Botanists who have worked on this 

 genus have usually been able to examine nothing more than a very limited 

 number of herbarium specimens, in the majority of cases without fruits, 

 and the classification which has resulted has been somewhat unsatisfactory 

 from the horticultural viewpoint. 



I wish to mention briefly the most important species or races which 

 are being studied here in Mexico, in order to give an idea of the present 

 state of the investigations. 



West Indian race. This seems to be the true Persea americana. In 

 order to determine this beyond the possibility of a doubt it will be necessary 

 to look up the original description of the species, study it carefully, and 

 ascertain from what regions the specimens were obtained upon which the 

 species was based. But as far as can be judged at present, the name 

 Persea americana was originally given to the kind of avocado which we 

 term the West Indian race. 



Several botanical varieties of this race have been created by botanists. 

 Of those which Meissner described in De Candolle's Prodromus the 



