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 to wander over the whole piedmont, but wherever possible they are driven some distance up a ravine or quebrada where it is hoped they will remain until morning. At daylight the muleteers gather tola bushes for fire and then set out to look for the mules, which may have strayed several miles from the camp and be quite invisible. When the cold is most intense they have to be watched part of the night and _ re- peatedly driven back to a selected pasture site; otherwise they start back on the home trail, and it takes half of the following day to recover them. At such times they stop feeding al- together, especially if the water is brackish, and, though fa- ticued by the day’s toil and by the effects of altitude, they nevertheless make their way along the trail at surprising speed. To awaken on a cloudy morning when the guides are anxious about snow and one is several days’ travel from the high passes on either side and to look about for miles in all directions and see not a sign of one’s transport animals is rather disconcerting in spite of the arrieros’ assurance that, “When the pot boils over the mules return from up the quebrada.”

In the long stretch from Rincon to Catua or Liri there is no grass—only shrubs, //areta (moss), and a very few lowly cacti. Among the grasses is the poisonous viscachera. Horses, mules, and asses die within two or three hours after cating it, even in small quantities. The Indians say that cattle and llamas are immune, but they probably do not eat it. All the muleteers know the grass and its distribution, and if they have to pass through it they drive their mules at a gallop to prevent them from eating it. Several times our Puna guides passed the mouths of ravines with apparently good pasture and water because the grass was poisonous; and there is constant talk among the guides of the localities where the vizcachera abounds. Out of one pack train of ninety mules seventy-five died as a result of eating it. It has been found to give rise in the stomach of the animal to prussic acid.

In the quebradas of the mountains are quetioa which some- times attains a height of four meters. Among trecs it attains the highest altitude in the cordillera and forms small groves in favored sites. Its trunk and branches are twisted. In places