1914] PETRY—OPHIOGLOSSUM PENDULUM 179 
pole of the root. At the same level, gaps appear in the sides of the 
cylinder (fig. 9, G, H,) and the xylem separates into two strands. 
The smaller of these (r, fig. 9, H) is the continuation of the original 
root, and at once resumes its original diarch character. The larger 
strand organizes itself into the stem stele. The three strands of 
the first leaf separate (fig. 9, 7, J), and at a slightly higher level 
(fig. 9, J, K) two roots are attached. The stem stele at this point 
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A J “Sap y, k®& << LL 
ants. 9.—Development of stem stele by medullation of root stele; only the xylem 
's shown: r, stele of parent root; rt, traces of first roots of new stem; /t, trace of first 
leaf; X25 
Consists of three strands (fig. 9, L), which organize the mature 
form of the stele in the usual way. In the other rhizomes showing 
manner of development, the original root is triarch or tetrarch; . 
after separation from the stem stele, the root stele usually shows 
‘n Mcreased number of protoxylem strands and the medullated 
condition shown in fig. 4. 
In all cases, the stem stele soon assumes its usual form, that of 
an ectophloic siphonostele with more or less overlapping leaf gaps 
