PILULARIA. 
289 
and stocked with miniature fish, is an object of intense 
interest. 
Genus XXIII. PILTJLARIA, or PILLWORT. 
The Pilularia glohulifera, Pill wort, or Pepper-grass, is 
a creeping-stemmed species, having filiform grass-like 
leaves, which grow in clusters at intervals along the thread¬ 
like stems, and bear the almost sessile fructification at 
their base. The parts of fructification differ considerably 
in position from those of Isoetes, in which the spore-cases 
are within the thickened bases of the leaves, while those of 
the Pilularia are quite free, and attached directly to the 
stem, though seated at the base of a small tuft of leaves ; 
they also differ in structure, that of Isoetes consisting of 
granular and pulverulent spores, occupying separate spore- 
cases, while in that of Pilularia the two kinds of spores 
are produced within each spore-case, the larger bodies 
occupying principally the lower, and the smaller ones the 
upper parts. 
The name comes from pilula, a little ball or pill, the 
spore-cases having a nearly globular form. 
