00305nam a2200109Ia 4500008004100000040003800041100001500079245004500094260002800139300001700167653001100184211214s9999    xx            000 0 und d  cJayakar Knowledge Resource Centre  aClausen, J 0aStage in the evolution of plant species.  bCORNELLaNEW YORKc1951  aXI, 203 p p.  aBOTANY