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 shm}^ 

 water in Avet 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. 



AYhile 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 fromx the cavities. During Januar}^ 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 httle 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 onty. 



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. Untersuchuneen tieber die Bedeutuns todter 

 Roehren und lebender Zellen fuer die Wasserbewesjung in der Pflanze. 

 5itz. d. K. Preuss. Ak. d. Wiss. zu Berlin. 1884: 1105-1117. 



