254 BOTANICAL GAZETTE [octopEs 
cell often branches, each portion giving rise to a disk (Pl. XXI/, 
jig. 42; XXII, fig. 4). Although the primary rhizoid usually 
remains short, in some instances it attains considerable length’ — 
before undergoing division or forming a disk (Pl. XXU/, figs. 37, 
38). While these changes are taking place, the cell adjacent to 
the basal cell sends out rhizoids similar to those arising from the _ 
primary root-cell (Pl. XX///, figs. 1, 5,6). These various root- 
filaments combine to form the primary holdfast, which is after- 
wards strengthened by multicellular branching rhizoids, springing 
from the basal corticating cells of the frond. The course of the 
filaments may be traced for some distance in the holdfast, but it 
is difficult to distinguish between those cells which have their 
origin in the primary disk and those which are derived from the 
corticating filaments. The difficulty in determining the relation- 
ship of the parts is increased by secondary lateral connections, 
which are developed between the corticating cells (PI. XXII, fg. 
43). The marginal cells of the mature holdfast are larger and 
broader in proportion to their length than the corticating cells 
of the frond, and have denser cell contents, but the chromato 
phores of both are separate disks, while those of the — 
siphon are the anastomosing filaments characteristic of hose : 
the Rhodomelacee. A creeping tendency may be exhibited : 
an early age, very young plantlets sometimes developing ™° 
distinct holdfasts of almost equal importance (Fl. XXIII ft 
As in the other species described, many branches arise pea 
massive rounded holdfast, probably springing adventitiony 
from the surface of the latter. 
A comparison of the three eee 
described will show that they agree in forming 4 primary disk: 
cell, which elongates into a rhizoid terminating ina eae a 
and in developing secondary rhizoids, which are sent ee 
root-cell, the cell adjacent to it, and the cortical ce = a 
of the frond. But, while the rhizoids of Polysiphoni r ia 
cellular, unbranched, and free, those of Dasya an pee 
multicellular, branched, and aggregated into a com : 
which in section resembles parenchymatous tissue. 
species of the Rhodomelace® 
pact Cc 
