•74 
as a protective structure, it loses' its. ecological, character, but usually 
maintains to a recognizable extent the characteristic form of the cells; 
in such cases, ..intercellular spaces are often formed by incurrent folds 
of the walls. In my notes such a structure is mentioned in P. accedens, 
P. revglutum, P.' Zippelii, P. dojichopterum, P. 17J/1 ( musaefolium ? ) , 
P. incur, vatum ; , P. commutatum, (fig. 32) , P. Phymatodes, P. Sclineideri, 
P. palmalum, P. angvstatum. P. albido-squanwtum, P. (Selliguea) cau- 
diforme (fig. 33), P . sinuosum (fig. 34), Lecanopteris (fig. 35), P. hera- 
cleum, Dryncma rigidula, I). quercifolium, Dryostachyum pilosum (fig. 
36), Thayeria (fig. 37) , and Pholinopteris. It also:, occurs in P. subauri- 
culatum; but is wanting in Taenitis and Cheiropleuria, and in P. a/ngus- 
tum, the type species of Pleopeltis. This is one reason why, if I were 
raising the subgenera of Poly podium to generic rank, I would keep 
Selliguea, , including Phymatodes, distinct from Pleopeltis. 
