192 A YEAR OF COSTA RICAN NATURAL HISTORY 



to the foot of the perpendicular fall, and with no more than 

 wet feet and slightly splashed clothing; we could see that the 

 floods of the rainy season had changed the positions of many 

 rocks and logs. On March 23 the quantity of water was 

 less than In February, while on April 26 It had Increased 

 •again in consequence of a rainfall unusually heavy for this 

 month. These fluctuations, trivial as they may seem, in the 

 volume of a stream which at best was relatively small, had 

 their efi'ect on the aquatic Insect and other animal life in- 

 habiting its course, the greater extent of surface water be- 

 low the fall tending to carry such creatures to lower levels 

 than the fall itself and so render them more accessible 

 to us. 



The farther waterfall was not more than thirty feet high 

 in its last stretch and fell Into a little basin five feet above 

 the level of the railroad, whence Its waters made their way 

 In a shallow ditch along the tracks for a quarter mile before 

 finding their way toward the Reventazon. Unlike the open 

 nearer fall, this waterfall was enclosed In a little recess well 

 shaded from the sun. Growing around it were begonias, 

 ferns, a delicate little Caryophyll {Stellaria ovata) and Urti- 

 caceous plants Including a species of Pilea and a coarse big- 

 leaved Myriocarpa, which we found blooming September 29. 

 The flowers of the Myriocarpa are borne In foot-long catkins 

 in the axils of the leaves. The stamens are curled on them- 

 selves and when ripe straighten out suddenly so that the 

 pollen is violently discharged In a little cloud to a distance 

 of several feet. 



On climbing to the top of this fall over the steep bank of 

 crumbling soil, one could, with the eye, follow the stream in 

 a series of low cascades. Two brooks in fact united just 

 above and descended through a tiny, dark moss-lined gorge. 

 Here, on August i, a pair of the delicate dragonfly Heterag- 

 rion chrysops was egg-laying In the gloom produced by the 



