The Critical Environment 



T. S. Roberts, Minnesota Museum of Natural History 



Fig. 1.4. Dead Lapland longspurs on the frozen surface of a Minnesota lake 

 after a late winter storm. 



Prescott, 1939, AAAS Pub. No. 10 



Fig. 1.5 Masses of dead fish washed ashore after the breakup of the ice in Lake 

 East Okoboji in northwestern Iowa. Bass, perch, carp, and other fish were killed 

 by the depletion of oxygen under the ice following the decay of a heavy growth 



of algae. 



