OF THE FILAMENTOUS ALGiE. 
75 - 
exhibit a peculiarity in the contraction of their cell walls 
when they are drying ; that is to say, the latter do not 
return to their former state when soaked in pure water 
but if a little muriatic acid or caustic potash be added to it r 
the cells immediately swell out to their original form. 
Should the filaments be encrusted with crystals of lime, 
they may generally be got rid of by means of dilute 
muriatic acid. 
There is one genus, Psichochorium, which has the 
remarkable property of depositing lime in the joints of its 
filaments. Special care must be taken to get rid of this 
when the specimens are being prepared, as, in case of their 
being left behind, the very parts become obscured and 
useless on which the generic characters depend. 
