ZYGOPHYTA. 129 
(9) Moisten a piece of perfectly fresh bread, and then sow here and 
there on its surface a few spores of Black Mould; cover with a tum- 
bler or bell-glass. In a few hours a new crop of Black Mould will 
begin developing. 
(2) The most common Black Moulds are species of the genus Mucor. 
M mucedo and M. stolonifer are common on many decaying sub- 
stances. M. syzygites occurs on decaying toadstools and other large 
fungi. Pilobolus crystallinus, Piptocephalis freseniana, and Cheto- 
cladium jonesii occur on animal excrement. Phycomyces nitens 
_ grows on oily or greasy substances, as old bones, oil-casks, etc. 
(¢) Place several clean glass slides in contact with a culture of 
Black Mould, as described in (g). By removing these at different 
times the various stages of growth of the mould may be easily 
studied. 
(j) Good specimens of Pond Scums may be made for preservation 
in the herbarium as follows: Place a tuft of the Pond Scum in a dish 
of clean water, and then by agitating the water for a few seconds the 
filaments may be made to sprea/ out in the water; now pass under 
the floating mass a sheet of heavy white paper, and slowly raise it in 
such a mauner as to lift out the plants with the least disturbance of 
their filaments. Allow the surplus water to drain off, then press the 
paper and specimens between sheets of heavy blotting-paper, first, 
however, laying a moist cotton or linen cloth over the specimen. By 
care such specimens will be found to adhere quite tightly to tlre 
sheets of paper. 
(k) Black Moulds may be obtained for herbarium specimens by 
placing cards or slips of paper in contact with cultures, and then re- 
moving them when the proper amount of mould has run over them; 
or portions of the mass as it grows upon a piece of bread—as in (g)— 
may be pressed lightly, and then glued to a sheet of paper. 
(@) For future study in the laboratory the aquatic zygoplvtes 
should be preserved in bottles of water containing just enough alcohol, 
glycerine, or carbolic acid to prevent their decay. One fourth or fifth 
of the first and second, and enough of the last to give a decided 
odor, will usually do well enough. 
