According to the observations of later botanists, the flowery crown of plants serves, among other things, to envelop the tender organs of fructification, and to protect them from the pernicious influence of external agents. Those organs of fructification are the chief objects of the maternal care of Nature; while shut up in the flower-bud, they acquire that strength and perfection of parts which enable them to endure the light of the sun, and to perform the functions for which they are designed. It is not till they are capable of fulfilling these functions that the flower unfolds itself; but it again closes at such times when external influences might be injurious to the delicate organs of fructification. Many flowers can bear only the refreshing morning air and the first rays of the sun, but remain shut all the rest of the day. This may be particularly observed in the different species of Convolvulus, Ipomæa, and Goat’s Beard. We find these, in general, open only till about eleven o’clock. In like manner, the Mallows and the Mesembryanthemums unfold their flowers about noon: and precisely at that time, in serene weather, open the singularly-formed Drosera, and the common Purslain, which shut again in an hour. Others unfold themselves only in the evening, and continue open all night, probably because their delicate organs would be injured by the sun. The Œnotheras, the Gauras, and the different species of the Mirabilis, furnish examples of this kind. Thus, too, the Cactus opuntia opens its magnificent blossoms at night only, and towards morning shuts them up for ever. The flowers of many plants of the nineteenth class are observed to hang their heads during night--the Camellia, for example--by which means the rain, or dew, which might injure the tender organs of fructification, can run off the more easily. In other plants of this class, the flower shuts up against rain, and on the approach of evening, as is the case with the Marigolds. The periodical change of colour in some flowers is also worthy of remark. Thus, the flowers of the speckled French Honeysuckle (_Hedysarum maculatum_) are purple in the morning and green at noon. The changeable Hibiscus (_Hibiscus mutabilis_) is white in the morning, flesh-coloured at noon, and rose-red in the evening. Thus, too, the great Corn-flag (_Gladiolus grandis_) changes its colour several times in the course of the day.