TYPES OF CRYPTOGAMS; THALLOPHYTES 245 
Note that in reproduction the cell-contents in many individuals 
has divided into two parts which become separated from each other 
by a cellulose partition. Each of these again divides, and the proc- 
ess continues until thirty-two or more cells may be found in one 
mass or they may fall apart at an earlier stage. 
279. Nutrition of Pleurococcus. — Plewrococcus can flourish only 
with an abundance of light and moisture. In daylight it can absorb 
carbon dioxide and fix carbon (giving off the oxygen at the same 
time as bubbles of oxygen) and can assimilate mineral substances. 
It is a capital example of an individual cell capable of independent 
existence. 
280. Motile Forms. — No motile form is known in Pleurococcus. 
Hematoccus, often known as Protococcus (Fig. 179), is a better object 
for study than Pleurococcus. It may sometimes be found in water 
of stagnant pools, particularly those which contain the drainage of 
barnyards or manure-heaps, in mud at the bottom of eaves-troughs, 
in barrels containing rain-water, or in water standing in cavities in 
logs or stumps. Its presence is indicated by a greenish or some- 
times by a reddish color. It is sometimes found in an actively 
swimming condition, in which case each cell is called a zodspore. 
THE STUDY OF VAUCHERIA 
281. Occurrence. — Species of Vaucheria are found in ponds, 
streams, and pools, immersed or floating like Spirogyra and at all 
seasons may be sought in greenhouses, where they grow on the moist 
earth of beds and pots, forming a green felt. 
282. Examination with the Magnifying Glass.— The magnifying 
glass will show the growth of Vaucheria to consist of numerous 
green filaments similar to those of Spirogyra. Select a small portion 
and spread out the filaments carefully in a drop of water on a slide. 
Does the glass reveal any indications of cross-partitions, of branch- 
ing, or of fruiting organs as short lateral branches? Does it show 
the form or arrangement of the green coloring matter? 
283. Examination with the Microscope. — Prepare as directed 
for the magnifying glass and place a cover-glass over the prepara- 
tion, with sufficient water. With the lowest power observe the 
