MORPHOLOGY 
whorls of branches arise. These branches are of two kinds: (i) those 
of limited growth, the so-called " leaves "; (2) those that resemble 
the parent axis in indefinite growth. The branches of limited growth 
form the whorl or rosette of branches at each node ; while usually in 
the axil of one of them the branch of indefinite growth appears. The 
axillary position of the main branch suggested that the smaller sub- 
tending branches are leaves. 
The main and lateral axes elongate by means of an apical cell (fig. 
114), which by successive transverse walls cuts off a longitudinal series 
of cells (segments). Each segment divides 
transversely into two cells, the lower one 
of which enlarges, forming the long inter- 
nodal cell (sometimes 10 cm. or more long), 
the upper one giving rise by successive di- 
visions to the plate of nodal cells, which 
develop the branches. In Nitella the long 
internodal cells remain uncovered ; but in 
Chara they become covered by a sheath 
of cells developed from the basal cells of 
the short branches, so that a cross section 
cell cutting off segments to form of an axis shows a central cell of large 
nodes^and internodes; the nodal caliber sheathed by a ring of small cells 
(cortical cells). The protoplast of the 
internodal cell consists of a thick peripheral 
layer of cytoplasm surrounding a large central vacuole and embedding 
numerous nuclei and oval chloroplasts. In a young internodal cell there 
is a single large nucleus, but in connection with the great enlargement of 
the cell the nucleus gives rise to numerous nuclei by fragmentation. The 
internodal cells of Nitella are noteworthy for exhibiting streaming 
movements of protoplasm with remarkable distinctness. 
Reproduction. No asexual spores are produced, but vegetative 
multiplication is secured by tuberlike outgrowths, special branches, etc., 
from the nodes. The structures connected with sexual reproduction, 
however, afford the most distinguishing feature of the group. The 
antheridia and oogonia, instead of being single cells, as in the groups 
previously described, are highly complex structures. They are borne 
at the nodes of the short branches and are visible to the naked eye, the 
mature antheridia being deep orange to red (fig. 115). 
Antheridinm. The antheridium is globular, the wall being com- 
FIG. 1 14. Chara : apical 
cells forming branches. After 
SACHS. 
