Before Linnaeus, the genera were the real units of the system. De
Candolle pointed out that the old common names of plants, such as roses
and clover, poplars and oaks, nearly all refer to genera. The type of
the clovers is rich in color, and the shape of the flower-heads and the
single flowers escape ordinary observation; but notwithstanding this,
clovers are easily recognized, even if new types come to hand. White and
red clovers and many other species are distinguished simply by
adjectives, the generic name remaining the same for all.
Tournefort, who lived in the second half of the 17th century
(1656-1708), is generally considered as the author of genera in
systematic botany. He adopted, what was at that time the general
conception and applied it throughout the vegetable kingdom. He grouped
the new and the rare and the previously overlooked forms in the same
manner in which the more conspicuous plants were already arranged by
universal consent. Species were distinguished by minor marks and often
indicated by short descriptions, but they were considered of secondary
importance.
Based on the idea of a direct creation of all [34] living beings, the
genera were then accepted as the created forms. They were therefore
regarded as the real existing types, and it was generally surmised that
species and varieties owed their origin to subsequent changes under the
influence of external conditions.
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