dent that very sudden thunder-showers often take such flowers by surprise, the previous state of the atmosphere not having been such as to give them due warning.
That parts of vegetables not only lose their irritability, but even their vital principle, in consequence of having accomplished the ends of their being, appears from an experiment of Linnæus upon Hemp. This is a diœcious plant, see p. 306, and Linnæus kept several fertile-flowered individuals in separate apartments from the barren ones, in order to try whether they could perfect their seeds without the aid of pollen. Some few however remained with the barren-flowered plants, and these ripened seed in due time, their stigmas having faded and withered soon after they had received the pollen. On the contrary, the stigmas which had been out of its reach continued green and vigorous, as if in vain expectation, nor did they begin to fade till they had thus lasted for a very long while. Since I read the history of this experiment, I have found it easy in many plants to tell by the appearance of the stigma whether the seed be fertilized or not. The above ex-
