Evans: HeEpatTicAE OF PUERTO Rico 561 
In 4. diffusa the lobule exhibits characters which are decidedly 
aberrant. As in the other species the line of attachment is very 
short, the free margin is involute near the base and the sinus 
passes gradually into the postical margin of the lobe. The free 
margin, however, instead of being straight or rounded in the apical 
region, is coarsely and sharply dentate. In normal cases three 
teeth are developed, the median tooth being larger than the others 
and sometimes attaining a length of ten cells and a width of seven 
or eight cells at the base. In rare instances a small additional 
tooth, proximal in position to the others, may also be demonstrated. 
In the few cases where the hyaline papilla was observed it occu- 
pied a position on the inner surface of the most distal tooth, close 
to the sharp sinus between this tooth and the median tooth. The 
remarkable peculiarities just described, taken in connection with 
the false dichotomy of the species, are perhaps sufficient to war- 
rant a generic separation of B. diffusa from Bryopteris. If it is still 
retained in the genus, the large median tooth must be considered 
the apex of the lobule, the tooth bearing the papilla would then 
be situated in what is morphologically the sinus, and the papilla 
itself, slightly displaced from the margin, would be distal to the 
apex, 
The leaf-cells are plane or slightly convex and vary consider- 
ably in size and in form in different parts of the lobe. In the 
basal auricles they are isodiametric, but in other parts of the lobe 
they are nearly always distinctly longer than broad (FIGURE 17). 
The largest and most elongated cells occupy a broad band in 
the postical part of the lobe, extending from the base (FIGURE 
18) to about the middle. These cells are often four times as 
long as broad but are never truly prosenchymatous. In the 
middle of the band they lie with their long axes approximately 
parallel, but they become more or less divergent as the incinlee 
boundaries of the band are approached. In passing from this 
band toward the margins and apex of the lobe, the cells gradually 
decrease in size and in relative length, some of the marginal cells 
being nearly isodiametric (FIGURE 19). The elongated cells thus 
form an indistinct false nerve, similar to those found in certain 
Species of Bazzania and Herberta. The cell-walls are practically 
Colorless and show well-developed local thickenings, which are 
