218 BRITISH PLANTS 
birthwort, rupture-wort, fleabane, gout-weed, lousewort, 
scabious, scurvy-grass, spurge, whitlow-grass. 
This nomenclature was clumsy and unsatisfactory. 
Many plants remained nameless. The names applied to | 
others were vague, referable to one plant in one district, 
and to another in another—e.g., the sea-purslane is either 
Arenaria peploides or Atriplea portulacoides. The same 
plant, too, had many aliases. In other cases a common 
name covered a multitude of species—e.g., buttercup, 
stonecrop, tare, vetch, violet. For scientific purposes 
this nomenclature was impossible. Besides, science is 
cosmopolitan ; it recognizes no race and no boundaries. 
What was wanted was a definite name for every plant, 
and one which botanists of all countries could use and 
understand. 
Many attempts were made to remedy this state of 
things, but the honour of founding a system of nomen- 
clature which was destined to be universally adopted 
belongs to Linneus, a Swedish botanist, the bicentenary 
of whose birth was celebrated all over Europe in 1907. 
He gave each plant two names, each thrown into a Latin 
form. The first was the name of the genus, the second 
that of the species. For example, there are many kinds of 
buttercups, all of which bear a strong family likeness to 
one another, especially in the flowers. Linnzus gave the 
generic name Ranunculus to the family group, and his 
description of the genus was an enumeration of those 
characters in which the various buttercups agree with 
one another. The genus as a plant does not exist ; only 
species exist. The genus is an abstraction, invented for 
the convenient purpose of denoting a group of species 
which possess many characters in common. Lach species 
agrees with the characters ascribed to the genus, but 
differs from every other species by one or more characters, 
which never vary. 
The classification of plants is based upon similarities 
and dissimilarities, but it is a matter of choice what par- 
ticular characters we select for comparison. Similarity 
very cften implies relationship, and this is especially true 
in the case of the flower—the most conservative part of 
the plant, and the part least affected by external condi- 
tions. Ina natural system of classification it is necessary 
to select those characters for comparison which denote 
