Punctuation, hyphenation, and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed. Inconsistent spacing in abbreviations was not changed.

Simple typographical errors were corrected; occasional unbalanced quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

Page 230: “spectrograph” was misprinted as “spectograph”; corrected here.

Page 315: “sporozooites” was printed that way.

Page 322: “uranium oxids” was printed that way.

Page 329: “‘Plant Geography of North American,’” may be a misprint for “America”.