This book is an attempt towards assessing the toxicity of certain pesticides on the survival of two free floating plants. Azolla cristata and Salvinia natans. In today's era pesticides and insecticides are ultimately finding their way into the aquatic ecosystems, hence posing a threat to the survival of the various plant and animal species inhabiting these systems. This book shall serve as basic guide to the researchers and students in understanding the toxicity of the widely chemicals on the plant diversity and survival.