Fig. 21. The figures illustrate in consecutive horizontal (transverse) sections the changes and 
rearrangements that occur in the vascular strands of the stem of Angiopteris. The corresponding components 
are similarly lettered throughout. 
A. The strands in a very young sporophyte ; B and C the same in older plants. 
a, b. Parts of the siphonostele at the edge of gap caused by the exit of a lower leaf trace. The 
reparation of the gap is shown in the later figures of the series A, B, C , respectively. 
c . The leaf trace strand to be given off to the next higher leaf, x (in series C), a commissural strand. 
To face p. 377. 
