424 Boodle and Hiley. — On the Vascular Structure of 
itself between the stele and the leaf-trace (the process beginning on the left) 
in such a way that the nodal mass of parenchyma (i. e. undifferentiated 
sclerenchyma) never comes into connexion with the cortex. The leaf-trace 
Fig. 1. Gleichenia circinnata. Transverse sections through a very young node. end. endo- 
dermis ; n.i. nodal island; p . pericycle ; ph. phloem. 1, 2, 3, 4 a, 4 b, 4 b', 4 b" , 5, and 6, proto- 
xylems. x 50. 
takes with it the protoxylems 4 b\ 4 b'\ and 5, leaving 4 a and 6 to supply 
the upper protoxylems of the stele (Text-fig. 1 4). 
The mature node differs from the one just described in having a group 
of sclerenchyma surrounded by an endodermis in the nodal island. In some 
of the cases examined this sclerenchyma became connected for a short 
distance with the cortex, but this is apparently not a constant feature. The 
