It flowers annually on the rockery at Kew.
The large difference between the means obtained at Potsdam and Kremsmtinster, as compared to the comparative similarity between the results for Kew and Karasjok, suggests that the mean value of the potential gradient may be much more dependent on local conditions than on difference of latitude.
The December and June curves for Kew are good examples of the ordinary nature of the difference between midwinter and midsummer.
The afternoon minimum at Kew gradually deepens as midsummer approaches.
At Karasjok and Kremsmunster the seasonal variation in a i seems comparatively small, but at Potsdam and the Bureau Central it is as large as at Kew.