7 6 





BOTANICAL GAZETTE 



[JULY 



*A 



Fig. 20 



Fig. 20. — L. Billardieri: photo- 

 graphs of the clay model, showing 

 the irregular behavior of the proto- 

 xylem groups and their relation to 

 the leaf traces; the protoxylem groups 

 here show both fusions and splittin 

 /, leaf trace. 



c* 



Fig. 



21 



Fig. 21. — L. Billardieri: photo- 

 graph showing an end view of the 

 model shown in fig. 20. 



