1913] PETRY—PROTOCORM OF OPHIOGLOSSUM 161 
which root formation is evidenced by at least an apical cell. A 
root usually attaches to the cylinder near the point of attachment 
of a leaf bundle. This produces a cross of vascular tissue, such as 
is shown in fig. 2. This relation of leaf bundle to root bundle is 
not invariable. : 
The ground tissue of the protocorm is a large-celled parenchyma 
similar to that of an ordinary rhizome. There are no intercellular 
spaces. The tissue within the vascular cylinder differs in no way 
from that outside. The cells everywhere are packed with food 
material, principally starch. 
Examination of the sections through the region immediately 
below the bottom of the central pit of the protocorm shows a 
Fics. 8-10.—Fig. 8, a transverse section of apical region of protocorm, 40” | 
below bottom of central pit: a, apical cell; 236; Fig. 9, a section 70 » below 
bottom of pit; Fig. 10, a section 95 » below bottom of pit. 
conspicuous apical cell, triangular in cross-section (figs. 7, 8, 9). 
This apical cell is an inverted triangular pyramid with strongly 
curyed faces. It is about 120 in length from vertex to center of 
base, and each side of the base is approximately 30 # in length. 
By reason of the strong curvature of the faces of the pyramid, 
the cross-section of the cell is greatest about halfway between 
vertex and base, where each side of a transverse section measures 
about 42 mu. 
The youngest segment of the apical cell has not divided. The 
next segment has divided twice longitudinally (figs. 8, 9, 10), and 
one of the resulting cells has divided once transversely, as shown by 
a count of the nuclei. The outlines of the third segment cannot be 
traced. 
