Studies in the Morphology of Selaginella pumila, Spring. 209 
also somewhat suggestive of the aerenchyma in the leaf- base of Miadesmia 
(11). This feature does not appear to have been noted before in the 
vegetative leaf. 
Fig. 20. Fig. 21. 
The epidermal cells of both surfaces are usually elongated, with sinuous 
lateral walls (fig. 19). The mesophyll of the leaf-blade shows no differentia- 
tion into palisade and spongy parenchyma (fig. 22). It extends right to 
the leaf-margin. 
Fig. 22. 
The vascular bundle in the cotyledons and lower leaves of the axis is 
simple, and consists of from four to five rows of delicate spiral and annular 
tracheides. It does not extend to the apex of the leaf, and, before dying 
16 
