80 



THE OPHIOGLOSSALES 



rhe trace foi the second leaf, the Inst functional one, is usually provided with 

 .1 single undivided bundle passing through rlu- petiole, hut sometimes this divides 

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

 hunille occurs in the petiole it occupies a nearly nu-dian position and is concentric 

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

 I he xylem consists of a huge mass oftracheids surrounded by the phloem, which is 

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

 in this portion wen- sieve tubes was not determined. \\ lure 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 hase of the leal, when- the ground tissue in 

 cross-section appears almost solid. 1 his development of lacunas in the first foliage 

 leaf recalls the similar ones in the cotyledons of Botrychium and Ophioglossum. 



In rhe 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 obviousl) associated with the leaf 

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



I i... 54. 



Three sections <>f an oldei orophytc <>f Helminthostachys. 8. The stipulai 

 sheath i- ab < i I From tin- third youngest leaf. 



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

 only causes tin- separation of tin- old leaves hut perhaps also acts as .1 protective 

 layei to the hat scais. I he absence of periderm from tin ventral side is no doubt 

 connected with the strictly dorsal position of the leaves. 



I he latei loots, like the first one, grow from a single teiiaheilr.il apical cell, 

 very much like that of Ophioglossum and Botrychium. I he root cap is not ver) 

 prominent and is usuall) somewhat pointed. It apparently owes its origin entireh 

 to the activity of the outei segments of the apical cell. Phe priman segments ol 

 the loot cap undergo periclinal divisions, hut, as in Botrychium, the stratifications 

 of the oldei la\eis 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 tin- three youngest segments shows six cells 

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

 the segments give use to the central cylinder of rhe root, while from the outei ones 

 is developed rhe cortex. As in tin- othei < >phioglossaceae, no root hairs are formed. 



