the writer in this second issue takes opportunity to correct sundry
errata, typographical and other, and at the same time to incorporate
such new information in reference to individual species and to the
subject entire as the researches of more recent years may afford.

To Miss Gulielma Lister, of London, the writer expresses his sense of
deep obligation for much assistance in settling difficult matters of
nomenclature and identification; it will be found as a result that in
most instances the same thing in the two volumes, English and American,
appears under the same name. There are still differences; these result
in most cases from different points of view, different estimates or
emphasis of characteristics in these ever elusive objects.

To Professor Torrend, formerly of Lisbon, the writer is indebted for a
set of European types, and to Professor Bethel, pathologist of Denver,
for rich material from the fertile mountains of Colorado and California.
To Professor Morton Peck, of Oregon, we are indebted for many notes of
the color of plasmodia and for collections of Pacific coast forms. Mr.
Bilgram, of Philadelphia, read the manuscript of the genus _Physarum_
and has contributed many rare species. To Dr. Sturgis, of Massachusetts,
we are indebted for material from both east and west.

The present volume is intended especially for American readers and is
accordingly particularly devoted to a discussion of species so far
reported on the western continent; nevertheless it has seemed wise to
include a brief description of some other forms as well, and reference
to many extra-limital species now generally recognized will be found
here and there in connection with the more extended treatment of related
American forms.

_February twenty-eight, 1921._

At the last moment, nearly all plates and drawings of the first
edition disappeared! necessitating a quick renewal of drawings
and plates. This may in part explain lack of uniformity, and
various minor irregularities sure to grieve the intelligent
student.

BIBLIOGRAPHY

The following are the principal works consulted in the prosecution of
the investigations here recorded:--

1763. Adanson, M. Familles des Plantes.

1805. Albertini--see under Schweinitz.

1841. Annals and Magazine of Natural History. London, various volumes:
1841, Ser. I., vol. vi.; 1850, Ser. II., vol. v.

1887. Annals of Botany, vols. i-xxxi.

1783. Batsch, A