Helminth ocladia - — Doty and Abbott 
61 
Thallus (Fig. 19) of cylindrical branches, 
9 cm. high, branching radial in the lower por- 
tions, the branches 4 mm. in diameter at their 
bases, gradually tapering to 1-2 mm. in diam- 
eter at the tips, strongly mucosoid. The main 
branches give rise laterally to shorter ones of 
irregular length between 1 and 3 cm. long. 
Basal disc 5 mm. in diameter. 
Cortical filaments (Fig. 20) up to 350 g in 
length, irregularly dichotomous or trichotomous, 
the lower cells ovoid to cylindrical, the terminal 
cells inflated and pyriform, 13-26.5 g wide X 45 
fx long. Short unbranched filaments, usually 
without the terminal pyriform cells, are com- 
monly borne at the tops of the cortical filaments 
(Figs. 21/, 24/). Numerous, sometimes branched 
rhizoids 7.2-12 ji wide are produced from the 
medullary filaments. Rhizoids are also produced 
(Fig. 21 r) by upper cells of the cortical fila- 
ments at first as protuberances 4.8-7. 2 /x wide 
on the lower edge of the cells (Fig. 22 f), then 
by elongation cutting off segments (Fig- 23 r). 
They are linear, unbranched, and seem to con- 
Fig. 19- The type of Helminthocladia rhizoidea, a 
single specimen preserved on a herbarium sheet. 
nect neighboring assimilatory branches to each 
other, whereas those rhizoids produced nearer 
the axial strand add thickness to the axis. Oc- 
casional hairs (Fig. 21 h) may be formed on 
the terminal cortical cells. 
Carpogonial branches 3 -celled, curved, mostly 
lateral as specially formed branches (stippled 
in Figs. 20, 23) at or near a dichotomy, but 
occasionally taking the place of a vegetative 
branch at a dichotomy. If unfertilized, they may 
develop into cortical filaments (Fig. 20) that 
are of smaller diameter than the ordinary cortical 
filaments. The first division of the gonimoblast 
is longitudinal. Gonimoblast dense, regular in 
shape (Fig. 22), soon becoming an irregularly 
shaped dense mass of filaments with only the 
end cells producing carpospores. 
A few sterile filaments are produced from the 
vegetative cells above the supporting cell (Fig. 
24) or from those subtending the supporting 
cell (Fig. 22). They loosely bracket and overtop 
the gonimoblast (Fig. 22/), together with the 
vegetative filaments deflected by the growth of 
the cystocarp. No fusion cell is formed. 
DISCUSSION: In its vegetative appearance ( Fig. 
19), H. rhizoidea is similar to certain other 
species of Helminthocladia, such as some forms 
of H. australis ( Desikachary, 1957 h, pi. 16, fig. 
3). It is a strikingly different alga from H. 
simplex, described above (Fig. 1 ) , which it does 
not resemble in either external or internal struc- 
ture. However it is generally similar in external 
appearance to other well-described species of 
Helminthocladia; i.e., H. calvadosii (Kylin, 
1930), H. papenfussii (Martin, 1939), and H. 
australis (Levring, 1953; Desikachary, 1957£). 
H. rhizoidea differs from these because of the 
production of decumbent rhizoids (r in Figs. 
21-23) from the basal ends of the vegetative 
cells, which constitute the assimilatory filaments. 
While this fact in itself may not be of first 
importance, it does clearly separate this species 
from other species of Helminthocladia. Rhizoi- 
dal structures do appear nearer the medulla 
in H. simplex ( Fig. 2 ) and in the Helmintho- 
cladia studied by Desikachary (1957 h: 442, fig. 
5), but these seem to have a different origin 
(see Fig. 18). It would seem that vegetative 
