The leaves of _robusta_ are much thinner than those of _liberica_, though not as thin as those of _arabica_. The tree, as a whole, is a very hardy variety and even bears blossoms when it is less than a year old. It blossoms throughout the entire year, the flowers having six-parted corollas. The drupes are smaller than those of _liberica;_ but are much thinner skinned, so that the coffee bean is actually not any smaller. The drupes mature in ten months. Although the plants bear as early as the first year, the yield for the first two years is of no account; but by the fourth year the crop is large. [Illustration: ROBUSTA COFFEE IN FLOWER, PREANGER, JAVA] [Illustration: COFFEE ESTATE IN THE LUQUILLO MOUNTAINS, PORTO RICO] [Illustration: JAPANESE LABORERS PICKING COFFEE ON KONA SIDE, ISLAND OF HAWAII] [Illustration: COFFEE UNDER THE STARS AND STRIPES] Arno Viehoever, pharmacognosist in charge of the pharmacognosy laboratory of the Bureau of Chemistry, United States Department of Agriculture, has recently announced findings confirming Hartwich which appear to permit of differentiation between _robusta, arabica_, and _liberica_.[97] These are mainly the peculiar folding of the endosperm, showing quite generally a distinct hook in the case of the _robusta_ coffee bean. The size of the embryo, and especially the relation of the rootlet to hypercotyl, will be found useful in the differentiation of the species _Coffea arabica, liberica_, and _robusta_ (see cut, page 142). [Illustration: ONE-YEAR-OLD ROBUSTA ESTATE, ON SUMATRA'S WEST COAST] Viehoever and Lepper carried on a series of cup tests of _robusta_, the results as to taste and flavor being distinctly favorable. They summarized their studies and tests as follows: The time when coffee could be limited to beans obtained from plants of _Coffea arabica_ and _Coffea liberica_ has passed. Other species, with qualities which make them desirable, even in preference to the well reputed named ones, have been discovered and cultivated. Among them, the species or group of _Coffea robusta_ has attained a great economic significance, and is grown in increasing amounts. While it has, as reports seem to indicate, not as yet been possible to obtain a strain that would be as desirable in flavor as the old "standard" _Coffea_ _arabica_, well known as Java or "Fancy Java" coffee, its merits have been established. The botanical origin is not quite cleared up, and the classification of the varieties belonging to the _robusta_ group deserves further study. Anatomical means of differentiating _robusta_ coffee from other species or groups, may be applied as distinctly helpful....