Ebony Spleenwort 81 
somewhat analogous to the highly developed leaves in Polystichum 
acrostichoides. 
The cleft pinnz are mostly unusually long, and commonly 
occur in the more central part of the leaf-blade, which is, as a 
rule, the most highly developed part of any mature leaf of this 
fern. The primary branches of the pinne’s midveins are mostly 
more complex in the cleft pinne than in the others, excepting 
those in the basal auricles of the latter, and constitute the seg- 
ment’s midveins. Series of sori occur along these midveins as 
well as along the pinnz’s midveins. In the uncleft pinne series 
of sori occur only along the pinnz’s midveins and the auricles’ 
midveins. The auricles, which, as already stated, are incipient 
segments, become basal segments in the cleft pinne. 
In this fern, as in A. angustifoliwm,* diplazioid sori, or dipla- 
zioid parts of sori, sometimes occur on veins that are both primary 
branches of one midvein and superior basal primary branches of 
primary branches of another. 
In addition to the incision described above, employed in the 
leaf’s development, slight incision, or a tendency to slight incision, 
between the leaf’s ultimate veinlets is often noticeable in the leaf 
at various stages. When present it adds to the unevenness of the 
leaf-blade’s margin, and in highly developed leaves causes the 
pinne’s segments to appear toothed. 
“Var. Horton”? Davenport is based upon monstrous leaves 
in which incision occurs in an extreme degree and is correlated, 
so far as known, with total sterility of the leaf. 
* See page 60. 
