80 THE OPHIOGLOSSALES 



The trace for the second leaf, the first functional one, is usually provided with 

 a single undivided bundle passing through the petiole, but sometimes this divides 

 into two, as it does in the cotyledon of Botrychium virginianum. Where a single 

 bundle occurs in the petiole it occupies a nearly median position and is concentric 

 in structure, although the phloem is somewhat less developed upon the adaxial side. 

 The xylem consists of a large mass of tracheids surrounded by the phloem, which is 

 reduced to about two rows of cells upon the adaxial side. Whether the largest cells 

 in this portion were sieve tubes was not determined. Where two bundles are present 

 they are somewhat smaller and are more nearly circular in outline than the single 

 bundle, which they resemble in structure. In the ground tissue are large inter- 

 cellular spaces which disappear at the base of the leaf, where the ground tissue in 

 cross-section appears almost solid. This development of lacunae in the first foHage 

 leaf recalls the similar ones in the cotyledons oi Botrychium and Ophtoglossum. 



In the older part of the rhizome there is a slight development of periderm on the 

 dorsal side, which Farmer found to be the case also in the older rhizome. This 

 periderm is restricted to the dorsal region and is obviously associated with the leaf 

 bases, as it is in Botrychium and probably also in Ophtoglossum. It presumably 



Fig. 54. 



Three sections of an older sforophyte of Hehninthostachys. X8. The stipular 

 sheath is absent from the third youngest leaf. 



acts as an absciss layer, such as Jeffrey demonstrated in Botrychium, and this not 

 only causes the separation of the old leaves but peihaps also acts as a protective 

 layer to the leaf scars. The absence of periderm from the ventral side is no doubt 

 connected with the strictly dorsal position of the leaves. 



The later roots, like the first one, grow from a single tetrahedral apical cell, 

 very much like that of Ophioglossum and Botrychium.. The root cap is not very 

 prominent and is usually somewhat pointed. It apparently owes its origin entirely 

 to the activity of the outer segments of the apical cell. The primary segments of 

 the root cap undergo periclinal divisions, but, as in Botrychium, the stratifications 

 of the older layers is much less marked than it is in the ordinary ferns. Each of 

 the lateral segments of the apical cell divides by a somewhat radially placed anti- 

 clinal, so that a transverse section of the three youngest segments shows six cells 

 having a nearly radial arrangement. Periclinal walls may arise and the inner cells of 

 the segments give rise to the central cylinder of the root, while from the outer ones 

 is developed the cortex. As in the other Ophioglossaceae, no root hairs are formed. 



