1914] PETRY—OPHIOGLOSSUM PENDULUM IgI 
lary strands of O. pendulum afford a much more definite case of this 
sort; they are in no way a traumatic response; cells of the pith 
develop a procambium which develops into xylem only; this may 
be taken to indicate that all cells of the pith are potentially xylem- 
producing, and therefore stelar. 
Summary 
1. The root stele varies from diarch to hexarch. The roots 
branch monopodially, and the branches are diarch at the base. 
2. Buds develop upon the roots in the same manner as in O. 
vulgatum. 
3. The rhizomes are always radial in structure; the leaves are 
inserted in an irregular spiral. 
4. The connection of the stem stele with that of the parent root 
is very variable ; no phylogenetic significance can be attached to 
the details of development of the stem stele of a bud. 
5. The stele of a mature rhizome is an ectophloic siphonostele 
with large overlapping leaf gaps; there is no secondary thickening. 
Root aps usually occur above the points of insertion of root strands. 
Incidental gaps not related to outgoing strands occur commonly. 
In a single large rhizome, numerous xylem strands occur 
within the pith. These arise from the inner surface of the cylinder 
°r aS procambium; some of them are concerned in the closure of 
leaf gaps, and others disappear as procambium or by fusion with 
the cylinder. They consist of xylem only. 
7. The vascular supply of the leaf consists of 3-12 strands, the 
number varying with the size of the leaf base. ‘These strands form 
@ cylindrical network in the petiole; in the lower portion of the 
blade, they constitute two series of strands with xylem oppositely 
directed. The strands with xylem abaxially directed form the 
vascular supply of the spike. 
The writer is indebted to Professor Joun M. CovuLTEr for many 
Suggestions and criticisms; and to Dr. CHARLES J. CHAMBERLAIN 
end. Dr. W. J. G. Lanp for the material used and for direction 
during the investigation. 
Tre University or CuIcaco 
