98 BOTANICAL GAZETTE [FEBRUARY 
exarch to mesarch, the later leaves from mesarch to endarch. 
Mature leaf traces are endarch. 
5. Apical meristems vary from the fernlike triangular apical 
cells in young sporelings to meristematic groups in older stems and 
roots. Such variation during the course of development occurs 
in the gametophytes of pteridophytes and in some liverworts, but 
is not recorded for the sporophyte of other ferns. 
6. The cotyledonary trace is collateral during most of its course. 
Later leaf traces start collateral and develop adaxial sieve tubes 
in their course through the cortex. Some stems show a slight 
tendency toward a reduction of internal phloem and endodermis, 
others an increase in the older part of the stem. The basis for 
classifying the Marattiaceae with pteridophytes that have devel- 
oped collateral bundles is therefore insecure. 
7. Secondary roots originate from vascular tissue before differ- 
entiation into regions has begun. The cortex shares in forming the 
cortex of the root. : 
8. Mucilage ducts originate both schizogenously and lysige- 
nously, generally the former. 
Marked instability is characteristic of Marattia. The Ophio- 
glossaceae share this trait in root structure, the Dicksonieae in 
protoxylem position. Only gametophytes have such a transition 
of apical regions. Combined with variability is the indefiniteness 
of the medullated monostelic stage. Such instability is character- 
istic of plants that give rise to new lines. It is evident that the 
Marattiaceae have retained many characters of the stock from 
which branched off the Ophioglossaceae, then the Psaronieae and 
Cyatheaceae. It is probable that the compact habit of the Marat- 
tiaceae was developed after the lines connecting with the other 
families had diverged, since the characteristics due to it are also 
unstable. 
This investigation was carried on at the University of Chicago, 
under the direction of Professor Joan M. Coutter and Dr. W. J. 6 
Lanp, to whom I wish to express my thanks for criticism and 
advice. 
Tue UNIVERSITY OF CHICAGO 
