766 THE AMERICAN NATURALIST. [Vol. XXXVIII. 



p. 219) is inclined to consider the radial type as older than the 

 dorsiventral, but as both types occur in both families under con- 

 sideration, this has little bearing upon the question of their rela- 

 tionships. 



In the structure of the apical meristems the Ophioglossaceae 

 are even more fern-like than the Marattiaceae, as they regularly 

 show a single tetrahedral initial in both stem and root. In this 

 respect they resemble the leptosporangiate ferns more than they 

 do the Marattiaceas. In the very young sporophyte of the lat- 

 ter, however, the root shows a single apical cell which is replaced 

 by a group of initials in the more massive roots of the older 

 sporophyte. 



The very complicated vascular system of the older sporophyte 

 in the Marattiacese is undoubtedly associated with the massive 

 stem. A study of the young plant shows that in the earlier 

 stages there is a single cylindrical stele much like that which 

 occurs in the adult rhizome of Helminthostachys and such lep- 

 tosporangiate ferns as Gleichenia. This is considered by Jeffrey 

 to be a primitive condition from which the more complicated 

 arrangement found in the adult stem of the Marattiaceae has been 

 derived. The arrangement of the vascular bundles in the stem 

 of Ophioglossum is much like that in the typical ferns, while 

 Botrychium closely resembles Osmunda. (Jeffrey, "Structure 

 of the Stem in the Pteridophyta and Gymnosperms," Phil. 

 Trans. 195, 1902.) 



The leaves of the Ophioglossaceae, which are in some respects 

 different from those of the typical ferns, nevertheless are much 

 more like these than like either the lycopods or Equisetaceae. 

 The venation is not essentially different from that of the Marat- 

 tiace;r, and aUhough there is never found the circinate form of 

 the y..uii- leal", so characteristic of the ferns, still in the larger 

 spccio of Botrychium tliere is an ai)proach to this which sug- 

 gests that the coiling of the young leaf is connected with the 

 very -reat development of the lamina of the leaf which charac- 



W hile the reticulate venation found in Ophioglossum is differ- 

 ent troni that m most ferns, still there are many ferns which 

 show a very smular venation. Thus among the Marattiaceae 



