i2o STUDIES IN FOSSIL BOTANY 



of the stele, as simple vascular strands, each of which 

 ultimately supplies one sporophyll. When about one- 

 third of the way through the cortex the trace divides 

 into three bundles, a median and two smaller lateral 

 strands (see the triple bundle It in Fig. 51). A little 

 further out the median bundle branches again, but this 

 time in a plane at right angles to the first division, so 

 that one of its branches lies above and inside the other 

 (see Fig. 51, on right; 1 also diagram, Fig. 49, v.b.). 

 The upper median bundle next divides into three, just 

 as the main strand had previously done, so that now 

 there are six bundles altogether, constituting each leaf- 

 trace, three above and three below ; all six enter the 

 base of the sporophyll, and pass out into its segments, 

 the three upper strands supplying the three sporangio- 

 phores, while the lower three enter the sterile leaflets 



(Fig- 49)- 



The bundle of the sporangiophore, on reaching its 

 peltate lamina, divides into four branches, which run 

 out to the bases of the four sporangia (Fig. 49,/"). In 

 the sterile lamina the vascular strand divides into two, 

 which enter the two apical points. 



The vascular system was thus a highly complex 

 one, corresponding to the great elaboration of the 

 external organisation. Each of the four sporangia of 

 a fertile segment is connected with the peltate lamina 

 by a neck of tissue (Fig. 50, s), into which the vascular 

 bundle enters, ending at the base of the sporangium 

 itself. The wall of the latter, which in its actual state 

 of preservation is only one cell thick, consists of long 



1 The reference -line to r crosses the median bundles of the trace 

 referred to. 



