Nov., 1908.] Air Cavities of Equisetum as Reservoirs. 
393 
THE AIR CAVITIES OF EQUISETUM AS WATER 
RESERVOIRS. 
John H. Schaffner. 
It is seldom that cavities in vegetative organs serve as reser¬ 
voirs for holding water. Schimper found that the large inter¬ 
cellular cavities in the swollen spindle-shaped petioles of an 
epiphytic Aroid, Philodendron cannifolium, are filled with slimy 
water in wet weather. He also noted that the water gradually 
disappears from the cavities during a dry period. 
Westermaier* described the cavities of Equisteum hyemale 
and E. telmateja as being full of water in winter and thought 
that the same condition might be found in summer also. Al¬ 
though Westermaier reported his observations in 1884, this inter¬ 
esting condition in Equisetum does not seem to be generally 
known. 
While walking through a deep ravine near Ziirich, Switzer¬ 
land, the past winter, I found a large patch of Equisetum hye¬ 
male in which to my surprise the cavities of the aerial stems were 
all turgid with water. The central cavities as well as the valle- 
cular and carinal cavities from the lowest to the highest inter¬ 
nodes were filled, and this was true for both old and young shoots. 
In many the water was frozen, especially in the lower joints. 
Some plants were pulled up and taken into my living room 
and by the end of the fourth day the free water had entirely dis¬ 
appeared from the cavities. During January numerous obser¬ 
vations were made. Usually the plants were found with cylin¬ 
ders of ice in the central and outer cavities. On January 14, 
most of the plants examined had little or no water in the central 
cavities but the vallecular cavities mostly contained cylinders of 
ice. Favorable plants were taken home and the bases placed in 
water. In nine days there was still some water in the lower parts 
of the central cavities of the middle internodes, but above and 
below the cavities contained air only. Plants with pieces of 
rhizome still had a little water in the bases of the central cavities 
on the thirteenth day, but at this time shoots without rhizomes 
contained air only. 
During the middle of May observations were made at Colum¬ 
bus, Ohio, on Equisetum robustum but even after a heavy rain, 
plants growing in very wet places showed no free water in any of 
the cavities. If the two species act similarly in this respect, it 
would seem that the water is present only during the cold period 
of the year and probably has some physiological connection with 
* Westermaier, M. Untersuchungen ueber die Bedeutung todter 
Roehren und lebender Zellen fuer die Wasserbewegung in der Pflanze. 
Sitz. d. K. Preuss. Ak. d. Wiss. zu Berlin. 1884: 1105-1117. 
