172 ABOUT HORSETAILS, [CHAP. 
These latter are evidently antheridia. The larger 
spores germinate by division of the cells of the apex, 
from which archegonia are formed. Fig. 130 repre- 
sents a leaf with its spore-case, which is also shown 
detached. Fig. 131 is a section of the spore-case 
showing the three chambers into which it is divided. . 
The plant is rare in the south of England. The 
name is derived from two Greek words, /sos, equal, 
and efos, a year, in allusion to its leaves, which are 
persistent during the whole year. 
The remaining species is known as P2/ularia globu- 
lifera, the Pillwort, or Pepper-grass. It grows on 
the margins of ponds and lakes, 
and presents the appearance of 
fig. 132. It has a creeping stem, 
from which, at intervals, are given 
off the fibrous roots which fix it 
in the mud, and the small quill- 
like leaves. These leaves are at 
first rolled up in a circinate man- 
ner, like the fronds of ferns, and 
vary in length from an inch to 
four inches. They are _ hollow, 
bright green, and smooth. 
The spore-cases are attached by 
a short stalk to the stem, at the 
base of the leaves. They are 
about the size of a pepper-corn, 
from which fact the popular name has arisen; they 
are densely clothed with hairs, and, when ripe, split 
open into four valves, to the centre of which the 
spores and antheridia are attached. The lower part 
