334 THALLOPHYTES 
From the nodes the branches arise in whorls and some branches 
resemble leaves, while others elongate much more and resemble 
the main axis. 
Their reproduction may be illustrated by following that of 
Chara. There are no asexual spores, but the plant is propagated 
vegetatively by special tuber-like branches which separate from 
the nodes and grow into new plants. 
Sexual reproduction involves complex structures which are not 
typical of Algae and which are the most distinguishing features 
of the Stoneworts. Both antheridia and odgonia (Fig. 287) are 
complex structures. Due to their size and color the sex organs 
are visible to the unaided eye. Both are developed at the nodes 
and often close together. 
The antheridium is an orange or reddish globular body with 
a wall composed of eight triangular plate-like cells. From the 
inner side of each of the wall cells there projects toward the 
center of the antheridium a much elongated cell which bears a 
terminal cell. The terminal cell, known as head cell, divides into 
a number of cells and each of these produces a pair of long fila- 
ments. Each filament consists of about 200 cells, each of which 
forms a single sperm. When an antheridium is fully formed, its 
interior is a tangle of filaments and the sperm output amounts 
to many thousands. The sperm is a much elongated ciliated 
structure, resembling the sperms of some of the more complex 
plants more than those of ordinary Algae. 
The odgonium with its jacket is larger and more elongated 
than the antheridium. The odgonia are often yellow but are not 
so brightly colored as the antheridia. An odgonium contains one 
large egg and much stored food in the form of starch and oil. 
The odgonium is closely invested by cells which grow up from the 
cells below and, as they elongate, wind spirally around the 
odgonium, forming a close jacket around it and a crown at 
its top. 
In fertilization the cells of the jacket spread apart at the 
crown, so that the sperms can enter. After fertilization the 
jacket hardens, and thus forms a nut-like case for the odspore. 
When the odspore germinates, it does not form a new plant 
directly but first forms a filament of cells, and the adult plant 
arises as a branch from this filament. This feature is prominent 
in the Bryophytes. 
