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LABORATORY STUDIES 183 
(Cosmarium) of a bright green color may frequently be found. 
The large lunate desmids (Closterium) are often more common. 
In the latter the clear protoplasm at each end is always stream- 
ing rapidly. 
(c) Round Diatoms may be obtained of dealers in laboratory 
material, or mounted slides may be used. A few Round 
Diatoms may be found occasionally in fresh-water ponds, and 
they often occur on the surfaces of marine seaweeds. 
(d) Collect a little of the brownish-yellow scum which in 
early spring gathers on the top of the water of brooks, ditches, 
and pools. Mount in water and examine with a high power. 
Hundreds of Flat Diatoms may be seen moving rapidly in 
every direction across the field. In any such preparation many 
species of various shapes will be found. The prevailing forms, 
however, are much flattened and somewhat diamond shaped 
in end view. 
(e) Study in like manner the slimy coating upon dead leaves 
and twigs in water in the summer for diatoms. On some of 
these very fine markings may be found. 
(f) Here again mounted slides of Flat Diatoms may be 
used with profit, but it is well to study living specimens so as 
to be able to observe their motility. 
(g) For future study in the laboratory the Conjugate Algae 
should be preserved in bottles of water containing just enough 
alcohol, glycerine, formaldehyde or carbolic acid to prevent 
their decay. One-fourth or fifth of the first and second, one- 
tenth of the third, and enough of the last to give a decided 
odor, will usually do well enough. A 2 per cent. solution of 
potassium acetate made light blue by addition of copper su)phate 
will preserve the green color of these plants, if kept in the dark. 
_ LITERATURE OF ZYGOPHYCEAE 
G. 8. West, A Treatise on the British Fresh-water Algae, Cam- 
bridge, 1904. 
Frank 8. Couuins, The Green Algae of North America, Tufts 
College, 1909. 
G. B. Dre Tont, Sylloge Algarum, Vol. II, Padua 1891-1894. 
H. VanHevurcx. A Treatise on the Diatomaceae (Engl. trans.), 
London, 1896. 
