352 Bottomley . — The Grozvth of Lemna Plants . 
♦ 
The experiments recorded show that Lemna minor and Lemna major 
are not able to grow normally in solutions containing inorganic materials 
only, but that the addition of certain organic substances to these solutions 
permits a rapid and healthy growth. These organic substances essential to 
the metabolism of the plants are to be found in the water of the ponds in 
which they normally grow, and maintain the plants in health, although lack 
of quantities of nitrates and phosphates in these conditions acts as a limiting 
factor retarding their rate of multiplication. 
