192. Forcing-houses have been long in use in Holland; but the date of their introduction we have not been able to learn. It is singular that they are not once mentioned in the early editions of Van Oosten, published from 1689 to 1750; but Adanson (Families des Plantes, preface), writing about the latter period, speaks of the hothouses of the Dutch in terms which evidently refer to forcing-houses. It is, however, questioned by some whether the Dutch had any forcing-houses, or hothouses, properly so called, as distinguished from pits and frames, previously to the introduction of the pine-apple. Before that period tanners' bark was employed by them for making forcing-beds. Miller says, the idea of employing tan for hotbeds was brought over from Holland, and that it was first used for raising orange trees in the beginning of King William's reign. It then fell into disuse, and afterwards was again applied to raising the pine-apple. The Dutch manner of forcing is still practised in some places in England.