CRYPTOGAMS 301 



circumstances arise, they begin again their work of repro- 

 duction and growth as actively as ever. 



339. Meaning of the name. — The suffix coccus is a Latin 

 noun (plural cocci) meaning a grain or berry, and is a general 

 term applied to any small, round organism consisting of a 

 single cell ; hence, micrococcus, a minute round body ; proto- 

 coccus, a primitive form, or prototype of one-celled bodies ; 

 and pleurococcus, which may be freely translated " a one- 

 sided little round body," from the flattening of the adjacent 

 sides during fission — pleuro meaning lateral, or pertaining 

 to the side. 



It is important to remember this definition, as the term 

 coccus is of very frequent occurrence in works of biology, as a 

 suffix for designating small round bodies of various kinds. 



340. Examination of a filamentous alga. — Place on a 

 white dish a few drops of water containing some of the green 

 pond scum comrrion in stagnant pools and ditches. Exam- 

 ine with a hand lens ; of what does it appear to consist ? 

 Are the filaments all alike, or are they of different lengths 

 and thickness ? Soak a number of them in alcohol for half 

 an hour and examine again ; where has the green matter 

 gone ? Do these algae contain chlorophyll ? (336 ; Exp. 65.) 

 This class are called filamentous algae on account of their 

 slender, threadlike thalli, which look like bits of fine floss 

 floating about in the water. The bubbles of oxygen which 

 they sometimes give off in great abundance cause the 

 frothy appearance that has given rise to their popular 

 name, " frog spit." 



341. Spirogyra. — ^ The filamentous algse are very numer- 

 ous, and a drop of pond scum will probably contain several 

 kinds. At least one of these, it is likely, will be a Spi- 

 rogyra, as this is one of the commonest and most widely 

 distributed of them all. Place a filament under the micro- 

 scope and notice the spiral bands in which the chlorophyll 

 is disposed within the cells. It is from this spiral arrange- 

 ment that the species takes its name. Do you notice any 



