For instance, the blue and red pimpernel, which are considered by most botanists as varieties, are said by Gartner to be quite sterile when crossed, and he consequently ranks them as undoubted species.

例如，被大多数植物学家认为是 pimpernel，Gartner 认为杂交后非常不育， 因此他将它们列为无可置疑物。