2 T 7 
Anatomy of the Ophioglossaceae. /. 
greater growth in length with extension of the leaf-trace departures and 
leaf-gaps. There may be an absolute decrease in diameter of the stem and 
stele as compared with the region below (Plant F), and in any case there is 
delay in assuming the full diameter of the adult region. In the plants 
selected for detailed examination the intermediate region only involved one 
or a few leaf-bases, but in other specimens it had a length of some inches. 
It appears as if intercalated between the basal and adult regions, possibly to 
bring the apex of the plant more rapidly to the proper depth below the 
surface of the soil. 
The degree of development of an internal endodermis in the inter- 
mediate region varies, as comparison of plants C, D, E, and F shows. The 
endodermal markings appear before the leaf-trace has separated and (like 
the reparatory band of endodermis formed in the departure of the early 
leaf-traces) the internal endodermis seems to be a new formation. While 
transverse sections in which the external and internal endodermis are con- 
tinuous show the appearance of an endodermal pocket described by Poirault 
and Bower, the reconstructions make clear that this appearance does not 
establish the existence of intrusive pocketing. In no case was a completely 
closed pocket found. Comparison of the mature structure of these plants 
thus leads to the conclusion that the internal endodermis, when present, 
is a new differentiation in the pith, and is of no morphological significance 
as indicating a limit between stele and cortex. 
The development of the stele from the apical meristem will not be 
dealt with in this paper. It may be said, however, that this has been 
carefully examined and no direct evidence in favour of an actual intrusion 
of tissue into the stele at the leaf-gap has been obtained. Since the dis- 
tribution of the endodermis when critically considered does not support the 
view of pocketing of the cortex into the stele, and direct evidence from the 
developing region is against any such readjustment of the tissues, it seems 
justifiable to conclude that the internal endodermis of Botrychium Lunaria 
is a new differentiation within an intrastelar pith. The association of the 
internal endodermis with the long leaf-insertions of the intermediate region 
suggests a physiological advantage in its presence, for it is found in regions 
in which there are long intervals between the roots and leaves. 
Some Details of the Vascular Anatomy of the Rhizome. 
The general construction of the vascular skeleton of the rhizome 
of Botrychium Lunaria has been considered in the preceding section. In this 
portion of the paper the structure of the stele in different regions of the 
stem will be described, especially as regards the xylem, and an account 
given of the structure of the leaf-trace until it enters the petiole. Further, 
the occasional development of xylem as a result of cambial activity 
