TAXONOMY 
241 
plant is rejuvenated by the formation of an auxospore. This may 
be formed with or without the conjugation of two parent-protoplasts. 
In either case the auxospore resulting undergoes a resting stage after 
which it develops new valves. The newly formed diatom is then 
several times the size of the individual or individuals which con¬ 
tributed to its formation and is endowed with renewed vigor for 
growth and division. 
6. Order Siphonales (, Siphon Alga). —This group is characterized 
by the peculiarity that the organisms constituting it possess proto¬ 
plasm containing myriads of nuclei within a common filament or 
cell cavity not segmented by cell walls. The term coenocyte has 
been given to such structures which consist of a many-nucleated mass 
of protoplasm surrounded by a cell wall. Some of the siphon algae 
reproduce by zoospore formation, others by conjugation as well as 
zoospore formation while Vaucheria, the green felt, stands out alone 
in reproducing both by the formation of a single zoospore and 
by the production also of oogonia and antheridia with resultant 
fertilization. (Fig. 113). 
7. Order Charales ( The Stoneworts). —Family Characeae.—The 
highest group of algae, possessing forms which are differentiated into 
stems/leaves and rhizoids. 
Chara , a type of this family, is a submerged fresh-water plant 
which fastens itself to the muddy bottom of ponds, ditches and slow 
streams by means of slender filaments called rhizoids. From these 
there arises a many noded (jointed) stem which bears whorls of 
slender green leaves at its nodes. Branches are also found issuing 
from some of the nodes which duplicate in appearance the main 
stem. Reproduction is either asexual or sexual. Asexual repro¬ 
duction is accomplished by means of tuber-like bodies borne on 
submerged parts or by special branches which form rhizoids on their 
lower nodes and later become separated from the parent plant. 
Sexual reproduction is effected through the formation of oogonia 
(female sex organs) and antheridia (male sex organs). These in 
some species are borne on the same plant; in others, on different 
plants. In all cases the sexual organs are produced at the nodes. 
The oogonium develops within itself a large ovum or egg. The 
antheridium produces within its wall numerous motile sperms. 
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