APRIL, 1908. LAKES AMATITLAN AND ATITLAN MEEK. 171 



water where they can get a foothold. In most places, especially next the 

 low lands, these plants are very abundant, usually growing to a depth 

 of 20 feet or more. They are usually submerged, though occasionally 

 the upper leaves or those in the shallow water float on the surface. 

 Two species of these (Potamogeton lucens and Potamogeton sp.) are 

 very abundant where found. Associated with these is a Hornwort 

 (Ceratophyllum demersum) , and two or three species of Char a are abun- 

 dant. These submerged plants are very important in connection with 

 fish food supply, since the absence of such plants means absence of the 



WILD LETTUCE, LAKE AMATITLAN 



small animals and insect larvae, as well as a decrease in the quantity 

 of algae. The tender portions of these plants furnish a considerable 

 supply of food for the smaller fishes in the lake. 



There is in Lake Amatitlan a considerable quantity of microscopic 

 organism, or Plankton, enough to prevent the water from being suffi- 

 ciently clear to see a white object a foot in diameter deeper than 12 or 

 15 feet. The Phytoplankton here much exceeds the Zooplankton; 

 in Lake Atitlan the reverse is true. In general the Zooplankton is 

 dependent on Phytoplankton for its food supply. The Phytoplankton 

 of Lake Amatitlan consists chiefly of algae. Closely allied to but not 

 properly included in Plankton are the larger forms of filamentous 

 algae. These are usually associated with the marsh plants and are often 



