Believes intermediate varieties are generally less numerous in individuals than the two states that they connect.

Discusses the difficulties of deciding what is the typical form of a species

and gives some opinions on the variability of introduced species compared with indigenous species.

Plants that are social in the U. S. but are not so in the Old World.

Distribution of U. S. species common to Europe.

Gives Theodor Engelmann’s opinion on the relative variability of indigenous and introduced plants and notes the effects of man’s settlement on the numbers and distribution of indigenous plants.

Outlines the ranges of northern U. S. species common to Europe. Hopes to investigate the resemblances between the floras of the north-eastern U. S. and western Europe. Discusses routes by which alpine plants appear to have reached U. S.