1921] WALKER—GAMETOPHYTES OF EQUISETUM 379 
ber 1908. Mrs, T. J. Frrzparrick also found large numbers of 
them on the banks of the Iowa River at Iowa City, Iowa, during 
the years 1884-1888. At Osborn, Indiana, Manhattan, Kansas, 
and Reno, Nevada, Professor N. F. PETERSEN found only a few 
specimens. At all other points, except Lincoln, they were present 
_ in large quantities. They were on the banks of every creek but one 
examined in the neighborhood of Lincoln, but were not abundant 
in any place. Mr. Nessir describes the habitat in which they 
grew at Tekamah, Nebraska, as follows: 
These were found along both banks of a typical prairie creek from the 
point where it emerges from the hills for a distance of at least four miles 
upstream. They occurred almost continuously throughout this distance. 
The creek is subject to overflow several times a year, and has built up a narrow 
floodplain of rich soil. ' The creek bed itself is about 15 ft. below the level of the 
floodplain, and is shaded by trees throughout most of its course. Near the 
water there is usually a belt of mud or very moist soil, varying in width from 
a few inches to several feet, and sloping gradually upward to the beginning of 
the more precip slope of the banks. ... . The gametophytes, varying in 
size from 1 I mm. to about 1 cm. in diameter, occurred on this mud. They were 
abundant, in many places being separated by an average distance of not more 
than 3 cm. In other places they were more scattered, and occasionally, 
where the mud belt was too soft, they were lacking entirely. ... . There 
were very few other plants growing in this mud belt, Riccia being the only 
form that appeared constantly. 
For all the localities in Nebraska, Kansas, and Iowa the same 
description in general holds true. They were found along streams. 
of all sizes, from the smallest creeks and drainage ditches to the 
Missouri River, and in all cases were on the mud belt and associated 
with Riccia. At Osborn, Indiana, the gametophytes grew in a 
ditch by a railroad on soil where ties had been burned. This had 
destroyed other vegetation, and mosses were just starting with the 
Equisetum. At Reno, Nevada, they were growing beside a waterfall. 
Identification of species 
In no case in Nebraska were mature Equisetum sporophytes 
found on the creek banks on which the gametophytes were growing. 
As a rule the only spore-producing plants within many miles were 
E. arvense and E. laevigatum, strictly prairie forms, Spores of 
E. arvense, E. robustum, and E. laevigatum have been grown in 
