1897] ALGAL STALACTITES OF YELLOWSTONE NATIONAL PARK 199 
these were formed in a similar manner to the stalactites already 
described. The stems must have first been out of the water, 
however, to allow the steam to condense on them. Afterwards 
the weight of the stalactites would draw them into the water. 
One of these stalactites preserved in formalin shows a length of 
45™™, a maximum width at the base of 12™", and a minimum 
width at the tip of 6™™. It is abruptly truncate at the tip, and 
is covered with a delicate green membrane, while the inner parts 
are lighter or whitish in color. In most cases these pendants 
formed a hollow tube closed at the tip. 
UNIVERSITY OF MINNESOTA. 
“EXPLANATION OF PLATE VIII. 
Fig. 1. View of stalactites zw sifu, natural size. 
Fig. 2. Cross section of a stalactite showing lamellae and hollow central 
portion. 
Fig. 4: Young filaments of Schizothrix calcicola. 
Fig. 4. Filament of same in later stage, with sheath containing two 
trichomes. 
Fig. 5. Cells of Glwocapsa violacea. 
Fig. 6. Cells of Synechococcus aeruginosus. 
Fig. 7. Stalactite formed by Phormidium laminosum. 
Fig. 8. Filament of Phormidium laminosum. 
