T913] PETRY—PROTOCORM OF OPHIOGLOSSUM 165 
(2) in the rhizome the upper and lower parts of a segment develop 
uniformly; in the protocorm the upper and lower parts of a segment 
grow unequally and the eversion of the corm results. 
CAMPBELL (8) states that in O. moluccanum there is ‘‘no reason 
for assuming that the tissues of the very open reticulum forming the 
fibrovascular system of the rhizome is in any part due to additions 
from the apical tissue of the stem.”’ As pointed out above, this is 
distinctly not the case in the rhizome of O. vulgatum, where the 
procambium strands are definitely related to the apical cell. It is 
to be noted also that the procambium of a leaf trace develops 
first at the point of connection of the strand with the cylinder. 
Summary 
1. The protocorm is nearly spherical, with a circular pit in the 
center of the top. This pit extends downward about o.8 of the 
diameter of the protocorm, and the apical cell is located at its 
bottom. 
2. The bases of the leaves are attached to the sides of this pit, 
_ with the oldest at the top. The functioning leaf is the seventh, and 
the primordia of six others occur below it. 
3. The vascular cylinder is an everted ectophloic siphonostele 
with endarch xylem. The leaf trace consists of two strands which 
attach separately to the cylinder. The roots are numerous and 
outside the cylinder. 
4. The apical cell is a triangular pyramid. The segments divide 
twice longitudinally before a transverse division occurs. The seg- 
ments enlarge below more rapidly than above, and the eversion of 
the cylinder results from this. 
5. The segments of the apical cell of a rhizome of O. vulgatum 
divide transversely first; the later divisions are irregular. The 
upper and lower portions of a segment enlarge uniformly. 
6. The vascular tissue of the rhizome is produced gd the apical 
cell directly, and is not made up of leaf traces. 
The writer is indebted to Professor Joun M. CouLTer for many 
helpful criticisms, and te Dr. W. J. G. Lanp under whose direction 
the investigation was made. The writer wishes also to express his 
thanks to Mr. W. A. Poyser for help in securing material. 
