190 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 t 

 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 pilWike sporocarps. 



