47 
sachusetts, the dates given are considered to be correct for the 
latitude of Boston or about 42 degrees north, and for the earlier 
species a few days should perhaps be added or subtracted in ex- 
treme northern or southern sections. 
This list, in its chronological features, is the outgrowth of five 
seasons of observation and inquiry, and although doubtless sus- 
ceptible of improvement, it is hoped to be a step in advance of the 
knowledge at present available on the subject, as our sources of 
information are often silent, indefinite, or altogether misleading. 
CHRONOLOGICAL LIST. 
May 5 — Equisetum arvense (fertile stems) Page 23 
“ 10 — Equisetum scirpoides 25 
“ 15 — Equisetum silvaticum (fertile) 24 
“ 20 — Equisetum hiemale 25 
“ 20 — Equisetum arvense campestre 24 
“ 25 — Botrychium simplex 20 
“ 25 — Osmunda Claytoniana (fertile) 17 
“ 30 — Equisetum litorale 24 
“ 30 — Osmunda cinnamomea (fertile) 17 
June 5 — Onoclea Struthiopteris (fertile) 14 
“ 5 — Equisetum fluviatile 25 
“ 5— Equisetum palustre 24 
“ 10 — Equisetum arvense (sterile) 23 
* '* 10 — Osmunda cinnamomea frondosa 18 
“ 15 — Equisetum variegatum 25 
“ 15 — Botrychium matricanefolium 21 
