I90 THE MARSILIACE^. 



merely a filiform petiole. The prothallia are very rudi- 

 mentary and develop with great rapidity. According to 

 Campbell they may develop from the spores and produce 

 mature sex-organs in twenty-four hours. 



There are nearly fifty species in the genus Marsilia, 

 mostly in tropical regions. Of Pilularia there are about 

 six species, widely distributed. Marsilia was named for 

 an early Italian naturalist, Aloysius Marsili. Pilularia is 

 from the Latin word for a " little pill," and is in allusion 

 to the small pill-like sporocarps. 



