Helminthocladia — Doty and ABBOTT 
59 
The terminal cell of the developing carpogonial 
branch is large at first (Fig. 3). Only three- 
celled carpogonial branches were seen (Fig. 15 
notwithstanding) . It often appeared (Figs. 5, 
6, 7) that the trichogyne cytoplasm became 
separated from the zygote cytoplasm; this we 
accepted as evidence that fertilization had taken 
place. Few cases were studied where we were 
certain that only the first division of the zygote 
had taken place. A number of cases were seen 
where two (Figs. 6, 7, 8), three (Figs. 9, 10, 
11), four, or five divisions (Fig. 12) had taken 
place. From these it was clear that division of 
the zygote is usually longitudinal or oblique, as 
in the case of H. papenfussii as illustrated by 
Martin (1939, figs. 17, 18). 
Conspicuous post-fertilization changes were 
not apparent in the carpogonial branch cells 
other than in those derived from the car- 
pogonium itself. No placental cell formation 
was seen. Pit connections within the carpogonial 
branch (Figs. 13, 14) and to the supporting 
cell and to the supra-supporting cell were not 
enlarged, or those between the carpogonial 
branch cells were only slightly enlarged. The 
hypogynous carpogonial branch cells in older 
stages (Figs. 13, 14) were "lighter staining” 
than during earlier stages. In the six or eight 
cases in older gonimoblasts studied in this re- 
gard (e.g., Fig. 15), the central complex of 
densely staining cells presumably derived from 
the carpogonial branch had only, at most, "broad- 
ened” pit connections. The contents of the sup- 
porting and supra-supporting cell were in some 
cases darkened and shrunken in diameter in this 
formalin-fixed material. 
As in H. papenfussii (Martin, 1939), Hel- 
minth ora lindaueri ( Desikachary, 1955: 131), 
and in Helminthocladia australis (Desikachary, 
1957&), encircling sterile rhizoid-like filaments 
(r in Figs. 6, 7, 9, 11, 14, 15) after fertiliza- 
tion grow especially around the hypogynous 
cells of the carpogonial branch. These were not 
seen to invade or surround older gonimoblasts 
of H. simplex when these were producing sur- 
faceward- growing filaments. In fact they seemed 
largely to have disappeared or become lost in 
our preparations of older stages. 
Gonimoblast initials appear from both pri- 
mary division products of the zygote (Figs. 
9-13). The cells of the young gonimoblast 
(Figs. 10-12) are at first in a dense regular 
mass which becomes lobed (Figs. 13, 14, 15) 
in time. In this respect our organism is like 
other Helminthocladia species and unlike other 
genera in the family. 
From the dense indefinitely lobed central 
gonimoblast mass, sparsely branched rather par- 
allel filaments (Fig. 16) grow towards the sur- 
face of the thallus. The gonimoblast filaments 
are usually unbranched for the terminal three 
cells. It may well be, though not followed out 
closely, that the terminal two cells tend to be- 
come carposporangia and the bottom (third 
one) gives rise (Fig. lib) to a two-celled 
branch that in turn grows to look like the 
terminal two cells of the parent filament be- 
fore they began enlarging into carposporangia. 
This same third cell may produce another 
branch. It is interesting to note this sympodial 
manner of growth here. 
In some cases the third cell in the row be- 
comes a carposporangium. In this respect the 
organism at hand approaches that condition 
illustrated by Kylin (1930, fig- 2D) for H. 
calvadosii. That is to say, there is nothing like 
the branching which Papenfuss ( 1946, fig. 25) 
illustrates for the homologous structures in 
Trichogloea . 
DISCUSSION: The type, MD 12691, is dis- 
tinguishable from the classical Helminthocladia 
hudsoni and H. calvadosii (accepted as the type 
species of the genus as circumscribed by Hamel, 
FIGS. 2-18. Reproductory and anatomical features of Helminthocladia simplex. 2, Cellular details of a 
cortical filament system bearing spermatangia (s) apically and a rhizoid (r) from the assimilatory region. 
3-5, Young carpogonial branches (stippled). 6—15, Stages in the development of the gonimoblast with its 
enveloping rhizoids. Individual cells are indicated by dark stippling; groups of cells are indicated by light stip- 
pling; enveloping rhizoids are indicated, and an assimilatory apical cortical cell. 16—17, Branching of the 
carpospore-producing filaments (b) . 18, Cellular details of a cortical vegetative filament system showing the 
strongly dichotomous branching and, from the inner cortical regions, rhizoidal filaments (r). 
