FRESH-WATER ALG. 215 
One curious species is found on windows and 
damp glass in shady places, where it forms round 
white spots, radiating like a spider's web from a 
centre, and sprinkled with minute, whitish, pow- 
dery particles. Another forms simple, trans- 
parent, club-shaped filaments, from a line to an 
inch in length, on the bodies of fishes and dead 
flies found on decaying leaves and weeds in the 
water. Several species are found in chemical solu- 
tions which are decomposed by them, in various 
infusions, such as distilled rose-water, dissolved 
muriate of barytes,and gum-dragon, and inorganic 
liquids undergoing fermentation, vinous, acetous, 
or putrefactive. The white flocculent matter often 
found on the surface of old stale ink, and the yel- 
low hyaline filaments found at the bottom of wine 
bottles, are referred to this class of plants, to which 
the generic name of Hygrocrocis has been given, 
from their byssoid nature, and the situations which 
they affect. All these spurious substances are now 
excluded from the list of alge. 
There is one species of alga, the saffron rock 
byssus (Chroolepis aureus), which deserves, on ac- 
count of its beauty, more than a passing notice. 
Unlike the other confervoid algze, which are found 
in moist situations or in water, it is restricted to 
the shady side of overhanging cliffs, trunks of 
trees, leaves and other objects, and never grows in 
