PF Se ee ee 
aC S72 ity lean ea 
Vol. 38 No. 4 
BULLETIN 
OF THE 
TORREY BOTANICAL CLUB 
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APRIL, IgII 
The genera of the fern tribe Vittarieae: their external morphology, 
venation, and relationships 
RALPH CURTISS BENEDICT 
(WITH PLATES 2-8) 
The fern tribe Vittarieae comprises upwards of one hundred 
species of simple-leaved tropical epiphytic ferns divided among 
six genera. The tribe is of particular interest because it includes 
in one of its genera, Monogramma Schk., two species which in leaf 
and stem structure stand at the bottom of the scale of vascular 
plants. In these species the leaf is a tiny threadlike structure 
with a single vascular bundle throughout its length. The stem 
has a central strand of xylem a few cells thick. The sporangia 
are borne along one margin in a deep groove. ‘It is hardly possible 
to imagine a simpler type of fern. 
The tribe, however, forms a connected series arranged upon the 
basis of venation pattern, beginning with Monogramma and ending, 
:n the most advanced genera, in a well-developed reticulate scheme. 
The species of the intermediate genera furnish all the intermediate 
steps between the two extremes. Furthermore, in the ontogeny 
of the more advanced genera the same series of venation patterns 
is repeated, affording a double chain of evidence by which the 
origin of this reticulate type can be traced. The stele varies from 
a tiny protostele in some of the species of Monogramma to an 
advanced type of siphonostele in Anetium et al. 
The tribe offers therefore an exceptionally good field for studies 
in comparative morphology and has also added interest due to 
[The BuLLETIN for March, 1911 (38: 103-152) was issued 7 Ap rgtt.] 
153 
