24 
Var. campestre Schultz, is a state in which the stem has both 
fruit and branches, the fertile stem sometimes having a few 
branches at the base, or, which is the more striking form, the 
branched normally sterile stem having a spike of fruit which is oc- 
casionally fertile. The latter form is most usual in sandy situa- 
tions, several hundred plants having been collected on a half acre 
of ground. Last two weeks in May. Europe. 
187. E. silvaticum L. Woodland Horsetail. Sterile and 
fertile stems nearly alike, 8-16 inches high, furnished with very 
slender compound, recurved branches ; stem about 12-furrowed ; 
branchlets three-toothed. Common along the borders of damp 
woods; nearly sterile in deep shade. “The prettiest plant in exist- 
ence.” — Shirley Hibbercl. Middle of May. Northern portions of 
the north temperate zone. 
Illustrated in Underwood’s “Our Native Ferns.” 
188. E. palustre L. Marsh Horsetail. Stems ail alike, 
1-3 feet high, sparsely branched, with about seven deep stria 4 , and 
sheaths with about as many white-margined teeth ; branches most- 
ly five-toothed. Marshes. Knight’s Island, Lake Champlain, 
Ezra Brainerd. Shore of Lake Champlain, Pringle; A. J. Grout. 
Abundant on the margins of St Johns river from the Aroostook 
northward, M. L. Fernald. Apparently confined to calcareous dis- 
tricts. Northern part of the north temperate zone. Early in June. 
V 
189. E. litorale Kulilewein. Stems of three kinds: 1 The 
normally sterile, 1-3 feet high, long caudate, often much 
branched. 2 — Stems, often numerous, somewhat shorter, and 
bearing small abortive spikelets. 3 — Stems 6 — 12 inches high, 
Avhich are stouter and bear larger spikes with spores often perfect. 
Stems 6-16 grooved ; sheaths loose, uppermost on fertile stems 
bell-shaped ; branches of two kinds, the four-angled hollow, the 
three-angled solid ' This plant is very variable and in eastern 
Massachusetts at least seems to intergrade between E. arvense and 
