Sykes.- — The Anatomy and Morphology of Tmesipteris. 71 
(e) Origin of Branch-Trace . The ordinary branch or c sporophylV trace 
is described by Bertrand 1 as arising by the passing out of a whole 
xylem group from the stele, the normal number of xylem-groups being 
then restored by the division of one of the remaining groups into two. 
Dangeard, however, does not discuss the origin of leaf- and branch-traces at 
Figure V illustrates the course of the xylem strands in the aerial stem, and is constructed 
from the series of cross-sections shown in Text* fig. VI, i-io, and taken at levels i-io in Text-fig. V. 
a, b, c, d = the xylem bundles, named in the order in which they give off traces. bt x , bt % , // 3 , bt x , 
bt 5 , bt 6 , bt 7 , bi 8 , bt 9 , bt 1Q = the traces given off; bt — branch-trace, It = leaf-trace; the dotted 
portion of any trace is that outside the stem stele. 
Figure VI, i-io, illustrates a series of cross-sections of the aerial stem through a region 
bearing one leaf and three fertile branches. Other branch-traces are also seen arising, and will 
supply branches at a higher level. {§ = gap, other letters as in Text-figs. IV and V.) In stages 1-5 
four xylem groups are present, but in stage 10 only three groups can be seen. The reduction in 
number has been brought about by both products of the division of Group b having passed out as 
branch-traces. This can also be more clearly understood in Text-fig. V. (Text-fig. VI is not drawn 
perfectly to scale.) 
any length, but asserts the similarity of the two, the chief difference con- 
sisting in the greater number of elements employed in the formation of the 
1 Bertrand, l.c., pp. 256-7. 
