CHAPTER TWENTY TWO.

  THE BAROMETER-TREE.

  After passing the _biscachera_, the trackers have not proceeded far,when Caspar again reins up with eyes lowered to the ground. The othersseeing this, also bring their horses to a stand; then watch the gaucho,who is apparently engaged with a fresh inspection of the trail.

  "Have you found anything else?" asks Cypriano.

  "No, _senorito_. Instead, I've lost something."

  "What?" inquire both, in a breath.

  "I don't any longer see the tracks of that shod horse. I mean the bigone we know nothing about. The pony's are here, but as for the other,they're missing."

  All three now join in a search for them, riding slowly along the trail,and in different directions backward and forward. But after someminutes thus passed, their search proves fruitless; no shod hoof-print,save that of the pony, to be seen.

  "This accounts for it," mutters Caspar, giving up the quest, andspeaking as to himself.

  "Accounts for what?" demands Cypriano, who has overheard him.

  "The return tracks we saw on the other side of the camp ground. I meanthe freshest of them, that went over the ford of the stream. Whoeverrode that horse, whether red or white man, has parted from the Indiansat their camping-place, no doubt after staying all night with them. Ha!there's something at the back of all this; somebody behind Aguara andhis Indians--that very somebody I've been guessing at. He--to a deadcertainty."

  The last sentences are not spoken aloud; for as yet he has not confidedhis suspicions about Francia and Valdez to his youthful comrades.

  "No matter about this shod horse and his back-track," he continues, oncemore heading his own animal to the trail. "We've now only to do withthose that have gone forward, and forward let us haste."

  While speaking he strikes his ponderous spurs against his horse's ribs,setting him into a canter, the others starting off at the same pace.

  For nearly an hour they continue this rate of speed, the conspicuoustrail enabling them to travel rapidly and without interruption. Itstill carries them up the Pilcomayo, though not always along the river'simmediate bank. At intervals it touches the water's edge, at othersparting from it; the deflections due to "bluffs" which here and thereimpinge upon the stream, leaving no room for path between it and theirbases.

  When nearing one of these, of greater elevation than common, Gasparagain draws his horse to a halt; though it cannot be the cliff which hascaused him to do so. His eyes are not on it, but turned on a tree,which stands at some distance from the path they are pursuing, out uponthe open plain. It is one of large size, and light green foliage, theleaves pinnate, bespeaking it of the order _leguminosae_. It is in factone of the numerous species of _mimosas_, or sensitive plants, common onthe plains and mountains of South America, and nowhere in greaternumber, or variety, than in the region of the Gran Chaco.

  Ludwig and Cypriano have, in the meantime, also drawn up; and turningtowards the tree at which Caspar is gazing, they see its long slenderbranches covered with clusters of bright yellow flowers, these evidentlythe object of his attention. There is something about them that callsfor his closer scrutiny; since after a glance or two, he turns hishorse's head towards the tree, and rides on to it.

  Arrived under its branches, he raises his hand aloft, plucks off a sprayof the flowers, and dismounting, proceeds to examine it with curiousminuteness, as if a botanist endeavouring to determine its genus orspecies! But he has no thought of this; for he knows the tree well,knows it to possess certain strange properties, one of which has beenhis reason for riding up to it, and acting as he now does.

  The other two have also drawn near; and dismounting, hold their horsesin hand while they watch him with wondering eyes. One of them criesout--

  "What now, Caspar? Why are you gathering those flowers?" It isCypriano who speaks, impatiently adding, "Remember, our time isprecious."

  "True, master," gravely responds the gaucho; "but however precious itis, we may soon have to employ it otherwise than in taking up a trail.If this tree tells truth, we'll have enough on our hands to take care ofourselves, without thinking of Indians."

  "What mean you?" both interrogated together.

  "Come hither, _senoritos_, and set your eyes on these flowers!"

  Thus requested they comply, leading their horses nearer to the tree.

  "Well?" exclaims Cypriano, "I see nothing in them; that is, nothing thatstrikes me as being strange."

  "But I do," says Ludwig, whose father had given him some instruction inthe science of botany. "I observe that the corollas are well nighclosed, which they should not be at this hour of the day, if the tree isin a healthy condition. It's the _uinay_; I know it well. We havepassed several on the way as we started this morning, but I noticed nonewith the flowers thus shrivelled up."

  "Stand still a while," counsels Gaspar, "and watch them."

  They do as desired, and see what greatly surprises them. At leastCypriano is surprised; for the young Paraguayan, unlike his half-Germancousin, unobservant of Nature generally, has never given a thought toany of its particular phenomena; and that now presented to his gaze isone of the strangest. For while they stand watching the _uinay_, itsflowers continue to close their corollas, the petals assuming a shrunk,withered appearance.

  The gaucho's countenance seems to take its cue from them, growing graveras he stands contemplating the change.

  "_Por Dios_!" he at length exclaims, "if that tree be speaking truth,and I never knew of the _uinay_ telling lies, we'll have a storm upon uswithin twenty minutes' time; such a one as will sweep us out of oursaddles, if we can't get under shelter. Ay, sure it's going to beeither a _temporal_ or _tormenta_! And this is not the where to meetit. Here we'd be smothered in a minute, if not blown up into the sky.Stay! I think I know of a place near by, where we may take refugebefore it's down upon us. Quick, _muchachos_! Mount, and let us awayfrom here. A moment lost, and it may be too late; _vamonos_!"

  Leaping back into their saddles, all three again go off in a gallop; nolonger upon the Indian trail, but in a somewhat different direction, thegaucho guiding and leading.