1913] PETRY—PROTOCORM OF OPHIOGLOSSUM 157 
irregular spiral approximating the 2 ee that has been 
described for this species. 
The vascular tissue a]l occurs above the growing point, that is, 
surrounding the circular pit from which the leaves arise (figs. 1, 2). 
Each leaf trace consists of two strands which connect separately 
with the vascular tissues of the corm. The roots extend in a general 
horizontal direction outward from the vascular tissue; three roots 
occur between the vascular tissue and the central pit, and run in 
a downward direction. 
ao 
Pie ema eg “¥ 
I, 2.—Fig. 1, diagram of longitudinal section through protocorm: 2, posi- 
tion of apical cell; c, cylinder strands; r, root strands; J, leaf strands; Fig. 2, 
erse section of protocorm, 3 mm. above bottom of pit: /, leaf primordium; 
Ft, petiole of functioning leaf . er cylinder strands; 7,r, root strands; /,/, leaf strands; 
a 
From study of the serial sections a model of the vascular sys- 
tem was built up in clay to a scale of 30 diameters. This was 
copied in plaster and photographed (figs. 3, 4, 5). 
As shown by these figures, the vascular tissue makes up a 
definite cylinder. Its structure will be understood from the 
following illustration. Suppose the vascular cylinder of an ordinary 
thizome of this species to be turned “wrong side out” by pulling 
the apical region down through the center of the stele, as one would 
pull the bottom of an inverted sack through the tubular part. 
This eversion of the stele of an ordinary rhizome of O. vulgatum 
