350 Davis . — On the Development of the Frond of 
tion seems about to push its way into this group of four initial 
cells. In Fig. 12, the first section of a plant *17 mm. long, the 
four original initial cells are not symmetrically arranged, and 
it is evident that the cell numbered 5, and perhaps also 6, 
would soon have become members of the first circle of initial 
cells. The first four sections of a plant *30 mm. long are shown 
in Fig. 13, and in that plant the tip may be said to have five 
initial cells. Probably the cells numbered 1, 2, 3, and 4 are 
the original four. Here the position of the cells numbered 
6, 7, 8, and 9 indicate that they will be, if they are not already, 
initial cells in the second circle. 
The young plant starts out with four initial cells. These 
were the cap-cells of the segmented spore. The initial cells 
cut off segments behind them, which divide rapidly and by 
their growth increase the area of the apex of the frond. The 
cells at the apex of the frond crowd one another, and some of 
them are forced to take position between the four apical cells. 
One or two of them usually wedge their way in between the 
four initial cells and finally become part of the first circle of 
initial cells. Other cells remain with their points placed 
between the cells of the first circle and take on the functions 
of initial cells and become the second circle of initial cells. 
A third circle of initial cells will be developed in a similar 
manner when the area of the apex of the frond becomes 
large enough to allow of its formation. After the groups of 
initial cells are well established the segments derived from 
each initial cell form files of cells radiating from the 
apex. 
The development of the hyphae and diaphragms will now 
be considered. I was very much surprised to find that they 
were the last structures of the frond to develop. It certainly 
seems that in Champia parvula they are developed some time 
after the initial cells have been differentiated and have as- 
sumed their function. The cells that are derived from the 
initial cells form a continuous tissue with the cells at the base 
of the plant, a tissue that is continuous with the cortex of the 
adult frond. This fact would seem to indicate that the hyphae 
