Anatomy of Acrostichum aureum. 185 
Such xerophilous features obtain in all the plants of the 
Mangrove swamps'—and are no doubt connected with the percentage 
of salt in the water,—but the adaptation is certainly more impressive 
here, in the leaf of a Pteridophyte which usually has a far simpler 
organization. The other species examined show a uniform meso- 
phyll and no hypoderm, while the stomates project from the surface, 
raised on a little dome of cells. 
Other Species of Acrostichum. 
For purposes of comparison several other species of Acrostichum 
have been examined. With the exception of A . criuitum, which is 
an erect-growing plant, these had all creeping rhizomes. All the 
species cut, however, without exception, showed a dictyostelic 
structure with a leaf-trace composed of two to five strands arranged 
in a simple loop (Text figs. 39 and 40). 
Figs. 39 & 40. Generalized diagrams of anatomy of stems of other species of 
Acrostichum. The three bundles of the leaf trace passing off. 
A. quercifolmm is the simplest. Its leaf receives two small 
strands which pass up the petiole unaltered. 
A. tomentosum, hybridum, conforme and. criuitum are very 
similar in behaviour. Usually about three strands pass off to the 
leaf, and these frequently soon divide to form five. 
The dictyostely of these species is very obviously related to 
solenostely, and evidently results from the over-lapping of the 
leaf-gaps. 
’ Areschoug. Untersuchungen der Mangrove-Pfianzen. Bibl. 
Bot. Heft. 56, 1902. 
