ANTS AND PLANT-STRUCTURE 391 



of Tococa, however, are inhabited by ants of medium 

 size, with a blackish or brownish abdomen and pale 

 thorax, and a milky fluid exudes from them when 

 crushed ; they bite but do not sting. 



T. macrophysca, Benth. (Spruce, 2188), grows in 

 moist caatingas of the Rio Negro and Uaupes, and 

 has leaves sometimes a foot long, not very unequal, 

 and all of them usually bearing a stout elongato- 

 cuneiform sac, an inch long, at the top of the 

 petiole. 



Tococas are scattered over the Amazon region 

 from the sea-coast to the roots of the Ancles, and 

 two species ( T. pterocalyx , sp. n., and T. parviflora, 

 sp. n.) ascend the Peruvian Andes to 2500-3000 

 feet. I gathered altogether twenty-four or twenty- 

 five species of Tococa, and all but one or two (T. 

 planifolia, Benth., and a closely -allied species or 

 variety) have sacs on the leaves inhabited by ants. 

 An examination of the circumstances of growth of 

 the esaccate T. planifolia seems to throw light on 

 the origin of sacs on the leaves of the other 

 species. 



Tococa planifolia grows here and there along the 

 shores of the Rio Negro, at least as far up as to 

 the foot of the cataracts, or say for about 700 miles. 

 From the cataracts upwards, on the main river, on 

 its tributary the Uaupes, and on some clear-water 

 affluents of the Casiquiari, it is replaced by an 

 allied non-sacciferous species or possibly a mere 

 variety. Wherever it grows, it always occupies the 

 very edge of the riparial forest, to which it forms 

 an inner fringe, along with various Rubiacese, 

 Apocynese, etc., of similar humble growth, all ot 

 which are completely submerged in the time of flood ; 



