100 BOTANICAL GAZETTE [| FEBRUARY 
the entire surface of the object. In this case the lime is depos- 
ited through exposure to the air of water containing a great 
abundance of calcium carbonate, and not through the agency of 
alge. 
It has not been proved that any one of the blue-green species 
or the Chantransia is able by itself to produce a separation of the 
carbonate, but two facts show the Chetophora to be independent 
of the others in its secretion of lime; first, its thalli are not 
engulfed in the substratum, and, second, the calcium carbonate 
is deposited in crystal plates instead of amorphous particles. 
Until recently the only additional inhabitants of the tank 
have been a species of moss, a Fontinalis, which formed a rich 
growth all over the bottom of the tank, and the little fresh- 
water shrimp, Gammarus pulex, which is present in exceedingly 
great numbers. During the latter part of the recent summer, 
however, the water has appeared less pure, and a heavy growth 
of Spirogyra spread over the surface. The blue-green alge 
remain unchanged, but the Chztophora has not thrived so 
well. It must be noted that not all the plants growing in the 
tank possess the ability to cause the precipitation of lime. 
Neither the moss nor the Spirogyra show a tendency to do so. 
In preparing a slide of the above material it is a good plan 
first to soak a piece thoroughly in water, then cutting off a thin 
section with a scalpel place in a dish of diluted hydrochloric 
acid and warm gently. When the bubbles of CO, cease form- 
ing, it can be mounted in water or glycerine. Before putting 
the cover glass in place, it is well to tease apart the filaments 
with needles, for the section is os to be too = for perfect 
transparency. 
iclleticks'calearcs, Tilden, Bex Alg. Cent. II. no. 165. 1896. 
(pl. IX., figs. 1-—3)—In extended strata either on surface of 
calcareous matrix, giving it then a brownish or sometimes a 
light eruginous tinge, or in layers throughout the matrix. Fila- 
‘ments 9-12.5m in diameter, erect, not rigid; pseudobranches 
appressed ; sheath rather thin, hyaline ; trichomes brown, some- 
times ee up to. fag ‘in 1 diameter, for the most Dae 
