1898 ] THE LEAF AND SPOROCARP OF PILULARIA f 
unbranched, This he was not fortunate enough to obtain, and 
it was left for Campbell (’93) to show that this was the case in 
P. Americana, where he found the sporocarp arose from a single 
cell at the base of the leaf. In the development of the capsule 
of the sporocarp in Pilularia, Juranyi thought the soral cavities 
arose by a splitting of the internal tissues of the young capsule, 
as Russow had described for Marsilia. Goebel on the contrary 
held that these cavities were external in origin, and this view was 
later confirmed by the work of Meunier and Campbell. 
According to Meunier’s work the young sporocarp is devel- 
oped from a two-sided (possibly a three-sided) apical cell which 
soon ceases to function as such, and growth is continued by the 
activity of four cells occupying the four corners of the tip of 
the sporocarp. Each of these cells was supposed to give rise 
to one of the four valves of the mature capsule with its sorus. 
Meunier’s figures of the vascular bundle system of the cap- 
sule and of the stalk show that the sporocarp is bilaterally sym- 
metrical, and that the plane of symmetry separates the sori into 
aright pair and a left pair and does not pass through the middle 
of diagonally opposite sori as do the longitudinal sections x dais 
by Meunier. 
The latest work on the development of the capsule ea: 
bell ’93 and ’95) indicates that one of the valves or lobes of the 
young capsule is developed directly from the apical cell of the 
sporocarp, being thus terminal in position, while a second appears 
lower down on the median line of the side toward the leaf, and 
the third and fourth on the right and left of this line respectively. 
This of course means that the plane of symmetry must pass 
through the upper and lower sori and between the other two, 
which does not agree well with the structure of the mature cap- 
sule of Pilularia as given by Meunier, or with the mode of 
development that I found in Marsilia. It was this difficulty in 
seeing how the structure of the mature capsule as given by 
Meunier could be developed in the manner described by Camp- 
bell that led me to take up the present work. 
According to my own observations the sporocarp of Pilularia 
