THALLOPHYTES 
and characteristically shaped chloroplasts. There is no reproduction 
by motile spores, and no motile cells of any kind are formed. Sexual 
reproduction is effected by the conjugation of protoplasts brought 
together usually through conjugating tubes, and while in a general way 
only isogamy is attained, there is evident in some forms an incipient 
heterogamy shown by the different behavior of the pairing protoplasts. 
The group as a whole seems to stand stiffly apart from all those previ- 
ously considered, and must be regarded as very highly specialized. 
(f) Chorales 
General character. The stoneworts, as these forms are called, con- 
stitute a very isolated group among thallophytes, which seems to hold 
no definite relation to any other 
group. If they are algae, they 
must be included among the 
green algae ; but they are con- 
sidered by many to be quite 
separate from algae ; and some 
would even remove them from 
thallophytes. Until something 
more is known of their relation- 
ships, however, it is convenient 
to consider them in connection 
with the green algae. They are 
found in fresh and brackish 
waters, attached to the bottom 
and covering large areas with a 
dense mass of vegetation. Some 
of the bodies are incrusted by 
such an abundant deposit of 
calcium carbonate that it makes 
them rough and brittle, and sug- 
gested the name stoneworts. 
The common genera are Chara 
FIG. 113. Chara: showing general habit 
of body. 
and Nitella, and the general 
structure is very uniform. 
Vegetative body. The vegetative body consists of a cylindric stem or 
main axis which branches profusely (fig. 113). All of the axes are dif- 
ferentiated into short nodes and long internodes, and from the nodes the 
