WATER EQUISETUM. 
57 
recorded in the ‘ English Flora, but the author remarks that 
he has seen no such variety in England. 
The barren stem is much longer than the fertile, and varies 
in an infinity of ways : among a few which I have lately gathered 
in the ditches of the Isle of Dogs, where this plant abounds, 
but can scarcely be said to flourish, I select the following as 
instances of variation. 
A — is forty-three inches in length, and has thirty-seven joints, 
without a single branch. 
B — is forty-five inches in length, and has forty joints : from the 
first to the nineteenth inclusive these are branchless, the twentieth 
has one branch, the twenty-first two branches, the twenty-second 
two, twenty-third to the fortieth inclusive one branch each. 
C — is forty-five inches in length, and has forty joints : these, 
from the first to the fifteenth inclusive are branchless, the six- 
teenth has one branch, the seventeenth has two branches, the 
eighteenth thirteen, the nineteenth eleven, the twentieth nine, the 
twenty-first nine, the twenty-second ten, the twenty-third ten, the 
twenty-fourth seven, the twenty-fifth eight, the twenty-sixth 
two, the twenty-seventh two, the twenty-eighth two, the twenty- 
ninth one, the thirtieth three, the thirty-first none, the thirty- 
second two, the thirty-third none, the thirty-fourth one, the 
thirty-fifth and thirty-sixth none, the thirty-seventh two, the 
thirty-eighth two, and the thirty-ninth and fortieth none. 
D — is forty inches in length, and has thirty- eight joints : from 
the first to the sixteenth inclusive, and also the eighteenth, twenty- 
fourth, twenty-seventh, twenty-ninth, thirty-first, thirty- third, 
thirty-fifth, thirty-sixth and thirty-eighth are branchless ; the 
seventeenth, nineteenth, twenty-first, twenty-third, twenty-fifth, 
twenty-sixth, twenty-eighth, thirtieth, thirty-second, thirty-fourth 
and thirty- seventh have one branch each, the twentieth has two 
branches, and the twenty-second three branches. 
It should also be observed that stems, which at first are per- 
fectly unbranched, often throw out a few scattered branches 
as the season advances, so that it is almost impossible to lay 
down any formula of branching that shall be at all constant. 
^ English Flora, iv, 326. 
