134 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Didymopanax micans. YAGRUME. 
An indigenous araliaceous tree known from the vicinity of Adjuntas, Cabo 
Rojo, and Aguada. (Urban, Symb. 1: 204.) 
Didymopanax morototoni. YAcruMe. 
Variously called * grayume’? or ‘ graymmo,” “ yagrume’” or ‘ yagrumo,”’ 
“yagrume macho,” and ** pana cimarrona.”’ A tree of 5 to 20 meters, probably 
the more common and widely distributed species in Porto Rico. ‘* Yagrumo 
macho” or ** male yagrumo’ alludes to the fact that this tree is believed to be 
the male of Cecropia, which is called ** yagrumo hembra.” 
Diffenbachia seguine. 
Family Araceae; a very succwent aroid from swampy meadows near Juncos. 
It grows from 3 to 6 feet (1 to 2 meters) high. 
Diego de noche. 
In Cuba Alfionia incarnata, 
Dioclea reflexa. Maro. 
Also called ** bejuco de mato.”” A leguminous vine climbing to the tops of the 
highest trees. Reported from Maunabo, Yabucoa, and Luquillo. (Urban, Symb. 
1: 473.) 
Diodia maritima. 
A rubiaceous herb. (Stahl, 5: 159, as Diodia radicaus.) 
Diodia radicans. See Diodia maritima. 
Diodia rigida. Diodia rigida. 
Family Rubiaceae; an herbaceous annual; frequents dry clay soil; 20 to 30 
centimeters high. (Stahl, 5: 84,) 
Diodia sarmentosa. Diodia sarmentosa. 
A woody herb growing among shrubs in arid soil; | meter high; from Maricao. 
(Stahl, 5: 86.) 
Diodia scandens. Drmopia TREPADORA. 
A woody herb, 1 meter high, found in dry soil. (Stahl, 5: 85.) 
Diodia trepadora. See Diodiau scandens. 
Dioscorea. Yam. Name. 
The true yams of the Tropics belong to a distinct botanical family, the Dios- 
coreaceae, related to the Smilax family and the Lily family, but having no affinity 
to the sweet potato, to some varieties of which the name is commonly applied in 
the South. Nearly all of the very numerous species form more or less thickened 
roots, and many of them have been introduced into cultivation, mostly in the 
Tropics. Some years since the Chinese yam, Dioscorea batatas, which is hardy in 
temperate climates, was advocated for general culture in Europe and the United 
States, but its habit of forming its tuberous roots 3 feet in the ground rendered 
it very difficult to handle by ordinary methods of agriculture. The tropical 
species have the same tendency, but usually not to so pronounced a degree, and in 
most tropical countries the yan is a more or less important article of diet. In 
some it is merely accessory to cassava, while in others it takes first place as a root 
crop. It seems certain that in Porto Rico they have received no such careful 
attention as in the British West Indies. and the following abridgment of a report 
on ** Yams in the West Indies,” recently furnished by Mr. David G. Fairchild, 
gricultural Explorer of the Section of Seed and Plant Introduction, United States 
Department of Agriculture, will probably be of use to those interested in agricul- 
ture in Porto Rico. 
It is important, of course, to plant the best sorts, but with so many species and 
varieties in cultivation it is difficult to tell the different forms apart or to know 
which is most desirable. At the Trinidad Botanic Gardens a series of experiments 
