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ary, I was obliged to leave La Paz on my journey to the Atlan- 

 tic. Thus, out of almost a year spent in this interesting region, 

 fortune had favored me with only about two weeks favorable col- 

 lecting. But extensive collections had been made meantime 

 upon the eastern slope at Unduavi and Yungas. Unduavi is one 

 of several little hamlets upon a mountain stream in the first valley 

 to the eastward of La Paz. But I have characterized by this 

 name the entire collecting station constituted by this valley and 

 its enclosing mountains. At 1 2,000 feet begins the semi-alpine 

 flora generally associated with Aspiditim aculeatum and the 

 smaller species of Acrostichum. At 10,000 feet the shining, 

 coriaceous leaves of the tropics begin to be seen, and at 8,000 

 feet the vegetation is truly tropical, including bamboos, fuchsias 

 and begonias. The whole surface is characteristically rocky, the 

 soil being very scanty indeed, but rich. At Unduavi, between 

 8,000 and 10,000 feet, I collected 150 species in flower in Octo- 

 ber, in three days. 



Crossing the northern wall of this valley, we find upon the 

 summit, at about 11,000 or i2,OQO feet, a cold, boggy and cloudy 

 region, where sphagnums and long drooping lichens abound. 

 Upon the other side we are in Yungas, referring not to the polit- 

 ical boundary, but to my collecting station of that name. De- 

 scending to 7,000 feet, we enter the great Andean forests which be- 

 come heavier and heavier, though scarcely denser, as we descend. 

 The trunks and greater branches are scarcely to be seen for the 

 epiphytes upon them, chief of which are orchids, bromeliads, 

 ferns, mosses and aroids. At 5,500 feet we strike the coca and 

 cinchona belt, and at 4,000 feet we find the heat becoming op- 

 pressive and the air sultry. From 3,500 to 5,500 feet is prob- 

 ably the region of greatest rain-fall. The Yungas collections 

 were chiefly made at elevations of 3,000, 4,000 and 6,000 feet. 



Leaving La Paz on the loth of January, 1886, we were at 

 once overtaken by the unprecedented rains of that season. At 

 Sorata, on the base of Mount Iliampu, we were detained by 

 floods from the latter part of January till about the first of March. 

 But little could be dried, and that little with the greatest diffi- 

 culty, many of the collections being repeated once and some of 

 them twice. In transit to the coast moreover, the continuous 



