42 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 
DISCUSSION OF RESULTS. 
We have restricted ourselves thus far to mere description of the develop- 
ment of Dennstedtia punctilobula. It remains to point out in order some 
general considerations suggested by the investigation. 
TAXONOMY. 
Whether our fern belongs in the Cyatheacez or the Polypodiacez should 
not be difficult to decide. The principal differences between the orders 
may be shown by a table: 
CYATHEACE. POLYPODIACEA. 
Annulus a complete circle, oblique. Annulus surrounding three-fourths of spo- 
Antheridium cover multicellular. rangium, symmetrical. 
Cushion of prothallus with bristles. Antheridium cover unicellular. 
Broad cells in continuous series in the rhi- Cushion without bristles. 
zogenous line. Rhizogenous cells separated by smaller 
cells. 
In all of these points the plant now under discussion agrees with the 
Polypodiacee. But Bauke (1876) states for Dicksonia rubiginosa that 
its antheridium is cyatheaceous. Moore (1857) and recent writers place 
D. rubiginosa Kaulf. and Dicksonia punctilobula Willd. in the genus Devn- 
stedtia. Gwynne-Vaughan (1903) further shows that D. rudbiginosa has a 
complicated solenostelic stem. If Moore and his followers are correct, 
the character of the antheridium must cease to stand as a distinction 
between the two orders. This point is much in need of investigation 
in other Dicksonias and Dennstedtias, as well as in Davallia, Lindsaya, 
Microlepia, and the allied genera. Cyatheaceous root-structure I have 
observed in Cibotium regale. But we need to know the arrangement of 
rhizogenous cells in the other genera just named. A knowledge of these 
points is especially needed for the Melanesian Dennstedtia flaccida, the type 
of the genus. For it may yet develop that our North American fern is 
not referable to the same genus with D. faccida. In that case we should 
have to adopt the generic name Sitobolium Desv. The point can only be 
settled after a careful examination of D. flaccida throughout its structure 
and life-history. The removal of our fern from the genus Dicksonia 
L’Herit. is generally agreed upon, and is quite sure to stand. The use of 
the name Dicksonia certainly leads to confusion, as when a recent European 
writer speaks of our plant as a ‘‘tree-fern.’’* But further studies along 
the lines indicated are needed to fully establish the position. Indeed, it is 
not impossible that such a comparison would break down the feeble barrier 
between Cyatheaceze and Polypodiaceze by showing a series of connecting 
links. 
*“Den nordamerikanischen, 2-3’ hohen Baumfarn.” Brick, 1897. 
