4i 
Anatomy of the Ophioglossaceae . 11L 
portion of the stele. This is most clearly seen on following the changes in 
the stele from below upwards, and this method also shows the intrastelar 
development of the pith which is naturally called in question on Campbell’s 
view. 
A further argument against Campbell’s interpretation is afforded by 
the vascular structure of the hypocotyl. In this region also the stele 
appears composed of a dorsal portion continuous with the first leaf-trace, 
and of a ventral portion. Apart from the fact that the ventral portion is not 
traceable into the second leaf (as would be necessary on Campbell’s view), 
it would appear a strained interpretation of the ventral and often larger 
portion of the stele below the first leaf, to regard it as due to the vascular 
strand entering from the next younger leaf; the latter was probably not 
developed when the vascular structure of the hypocotyl was determined. 
This question has been discussed at some length because the interpreta¬ 
tion of the vascular structure of the Ophioglossaceae given by Campbell has 
wide bearings on the general morphology of vascular plants. His view is 
in accordance with a phytonic theory, and while applicable with some 
difficulty to the stelar structure in Ophioglossum , meets with greater 
difficulties in the stele of the shoot of Botrychium t which is also radially 
constructed. It appears to be almost negatived when the attempt is made 
to apply it to the dorsiventral shoot of Helminthostachys , where there is 
a ventral component not bearing leaves. 
On the alternative view held in this paper, the segmental construction 
of the shoot is recognized, but is not regarded as inconsistent with the 
primary existence of an axis upon which the leaves arise as lateral 
appendages. Both the segmental construction of the shoot and its morpho¬ 
logical unity require to be recognized. Phytonic theories may be said to 
over-emphasize the first feature, while opposing views tend to minimize the 
reality of segmental construction. This general aspect of the question 
cannot, however, be further discussed here. 
5. Concluding Remarks. 
In the first number of these studies, 1 the direction which a number of 
features of the rhizome of Botrychium lunaria indicated for the relationship 
of the Ophioglossaceae to other plants was very briefly considered. The 
general view expressed was that ‘ the stelar structure, the medullation, the 
construction of the leaf-trace, and the nature of the branching, are all 
consistent with a relationship of the Ophioglossaceae to the ancient Fern 
stock, the general features of which are indicated in the relatively primitive 
groups of Ferns, such as Zygopterideae, Botryopterideae, Osmundaceae, 
Hymenophyllaceae, &c.’ This is in general accord with the views expressed 
by Renault and Scott, 2 and with the position now given to the group by 
1 Loc. cit., p. 240. 2 Studies in Fossil Botany, p. 640. 
