THE WILLIAMSONIAS OF THE MIXTECA ALTA 
G. R. WIELAND 
(WITH TEN FIGURES) 
The great plateau and mountain region in the central and western 
portion of the southern Mexican state of Oaxaca is commonly known 
in Mexico as the Mixteca alta, or high country of the Mixteca Indians. 
This name is used in contradistinction to the Mixteca baja, or portions 
of the lower country or tierra caliente over which the Mixtecas have 
extended. Simply speaking, then, the Mixteca alta is a portion of 
the southern edge of the Cordilleran system facing the Pacific and 
extending through western Oaxaca to the border of Guerrero, or into 
the latter state. Here, during some five months of the past winter 
and spring I have had the pleasure of continuing field work on the 
American fossil cycads under the auspices of the Instituto Geologico 
Nacional de Mexico. I have the kind permission of the director, 
Sefior AGUILERA, to note in this preliminary manner that the results 
obtained are regarded as of the greatest interest to paleobotanists. 
The field work has included the making of an accurate section 
through fully 2000 feet of plant beds of Rhit-Liassic age, full of 
cycads in as great a variety of types as has thus far been encountered 
anywhere in the world. Indeed, considering the fine material ob- 
tained from the localities noted in the valley of the Rio Nochixtlan 
hear Tlaxiaco, at Mixtepec on the Rio Tlaxiaco, notably all around 
the Mina Consuelo, about El Cerro del Lucero, and the Rosario region 
to the southwest of Tezoatlan, as well as elsewhere, and considering, 
Moreover, the almost endless opportunity for opening up quarries in 
all this extensive country, I am of the opinion that the Mixteca alta 
IS one of the most promising and accessible regions for the student of 
fossil plants yet discovered. 
True enough, these localities are distant from the railway 50 to 
150 miles or more, over the roughest of mountain trails. And as 
Mountain succeeds mountain with scarce a valley between, there are 
Some real difficulties for the collector, who must send out his material 
in blocks of limited size, such as can be loaded on the backs of the 
427] [Botanical Gazette, vol’ 48 
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