183 
to restore each cell to its original size, and thus throw the ring 
back to its original position. He thinks the bubble is formed of 
the air contained in the cell sap. If this be the case, as the 
amount of air is a very small per cent. of the cell contents, even 
should it expand, its pressure could not be so great as that of 
the surrounding denser air. It is difficult, moreover, to under- 
stand why the air in the cell should expand, as there is no dimin- 
ution of external pressure nor any rise of temperature. The 
third movement he accounts for by the further evaporation from 
the cells. y 
A clear explanation of the causes which produce the dehis- 
cence in the fern sporangia remains to be worked out. The 
presence of the lip-cells here described, of the existence of which 
M. du Sablon’s figures and descriptions give no recognition, may 
prove an important factor. 
BOTANICAL LABORATORY arte tae 
OF MICHIGAN, June, 1887. 
{For other notes on this subject see the BULLETIN xiii, p. 168, ; Ber. Deutsch 
Bot. Gesell., iv, p- 42; Journ. Roy. Mic. Soc. 1886, pp. 828 and 1020 ; 1887, p. 662 ; 
and Flora, Ixx, (1887) pp. 177, 192, 202-208.—Ep. ] 
Notes on the Flora of Cayuta Creek. 
Being stationed for a few weeks at Waverly, N. Y. (Tioga 
Co.), near the mouth of this stream, I determined to work up its 
bed and shed as far as possible, it being an especially interesting 
locality to me, as it geographically connects my work in Broome 
Co, with that of Dr. Lucy in Chemung Co., and of Prof. Dudley in 
the Cayuga Lake Basin. This little rivulet, having its source in 
a small lake by the same name situated a little south of east of 
the head of Seneca Lake and between it and Cayuga, flows south- 
east for half its length and then mainly south to its junction with 
the Susquehanna river, just across the Pennsylvania State line, a 
little east of the center of the southern tier of counties. This 
stream is about 35 miles long, flows through a narrow valley 
whose hillsides are mostly cleared and form fine farm lands, and 
forms a natural county line between Schuyler and Tompkins on the 
north, and Chemung and Tioga on the south.* Thus far we 
* Those who are fortunate enough to possess Prof. Dudley’s ‘‘ Cayuga Flora,”’ 
will find a quite faithful map of this location as a frontispiece. 
