TAXONOMY 
191 
the siliceous case separate into two distinct masses and the valves 
separate slightly from each other. As the two daughter-masses 
become more and more developed, the valves of the parent-cell are 
pushed more widely apart. Each of the two masses secretes for 
itself a new valve on the side opposite to the original valve. When 
the process is completed the girdle of the parent-diatom separates 
and the two daughter-diatoms thus become independent plants. 
Each of these possesses one of the parent valves and a second, which 
it has formed itself more or less parallel to the first. 
In a number of species, repeated fission results in the formation 
of succeedingly smaller and weaker individuals. This process, 
however, goes on only for a certain number of generations until 
the decrease of size has reached a limit for the species, when the 
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. 
5. 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 canocyte 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 Vancheria, 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. 
6. 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 
