73 
accedens. Drymoglossum and Niphobolus are unmistakably related, and 
Elaphoglossum is probably parallel in genesis to Niphobolus, with a 
reasonably near common ancestor. Elaphoglossum is no small genus 
in the Philippines. 
Prom the Graspedaria group are descended the species of Phymatodes 
with more ample, entire fronds, among which several natural groups 
are more easy to recognize than to define. Prom one of these, perhaps 
from some such fern as P. triquetrum, the Selliguea group is derived. 
More than one of these groups with entire fronds has descendants with 
the fronds deeply pinnatifid, as in P. phymatodes. One of the most 
natural of the latter groups with the fronds almost pinnate, is exceedingly 
thin in texture, and inhabits water courses and very moist banks. 
Among its species are P. insigne and P. dolichopterum. P. ellipticum 
is an outgrowth of this group, and is, therefore, not intimately related 
to the other species called Selliguea. Another group of the pinnatifid 
species includes P. incurvatum and P. palmatum. The former is de- 
cidedly dimorphous, and strongly suggests the probable ancestry of 
Ghristiopteris. Gheiropleuria, too, has possibly its source here,, but I 
strongly suspect that both it and Taenitis are Aspidioid in origin. An- 
other group in Phymatodes is Myrmecophila (Aspidopodium) , the com- 
monest species of which is. P. sinuosum. This group has given rise to 
Lecanopteris. 
Finally, the most diversified and highly specialized outgrowth of 
Phymatodes is the Drynaria group of genera. Within the usually ac- 
cepted limits of Phymatodes, P. musaefolium and P. ( Drynariopsis ) 
heracleum lead to this group, from the large group of species with 
ample, entire fronds. Prom some such plant as P. heracleum, Drynaria 
has evolved by the restriction of the humus-collecting work to distinct 
fronds. Prom a similar ancestor, Aglaomorpha and Dryostacliyum have 
been evolved by the restriction of the fertile region to the apex of the 
frond and the fusion of the sori. Prom these, Thayeria, the most highly 
specialized of the group, has probably been derived. The Drynaria 
group is a very natural one, characterized by its habit, by the fleshy 
rhizome, and its scales, by the frond form (exception, D. rigidula) and 
venation, and by the remarkable cutting-off of the segments. ■ Photinop- 
teris is a probable relative of Dryostachyum, the affinity being indicated 
by the location of the fertile region, absence of definite sori, and the 
glands at the bases of the pinnae ; young fronds- of D. pilosum have rows 
of lime dots. 
The Phymatodes group, as a whole, is xerophytic and characterized 
by the presence of a specialized hypodermis beneath the upper epidermis. 
The cells of this tissue are irregular in surface view, very often more 
so than the epidermis; sometimes one, sometimes the other has the 
thicker walls. Under conditions that render the hypodermis unnecessary 
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