XEROPHYTES, zer'd-fits, plants which have guarded themselves by structural means against excessive transpiration. The term was originally applied to plants living in dry and sandy soil, or on rocks, and to those in habiting deserts; but it is now extended to plants existing in localities where, for one reason or another, they cannot readily obtain water, as in the case of the vegetation in salt marshes, arid hogs and moors and of cold regions where water is present but not asail able for the use of the plants, which have consequently adapted themselves to prevent the waste of the moisture which they have. This result is obtained in various ways. In some, the transpiring surface is greatly reduced, and the foliage is nearly or wholly dispensed with, the stems themselves taking its place, as in switch plants and cacti; and this habit is fre quently combined with the storage of water in succulent tissues Other plants, like the eu calyptus trees predominating in the dry forests of Australia, by a vertical arrangement of their foliage. or a similar disposition of the
branches themselves, when foliage is wanting, as it is in the casuarinas. avoid presenting broad surfaces to the sun and hot winds Some erophvoc plants close their leases just before the cit.) season; the whole existence of others begins and ends during the continu ance of a rainy season; and in the bulbous and tuberous plants we see still another cow mon arrangement for passing the dreaded dry months, the plants growing vigorously and completing their above-ground existence, while the weather is still favorable, and storing up food in their roots or rootstocks, su that they may rest uninjured in the ground during the heated term, and be ready to spring into acti ity as soon as the rains begin. An extensoe development of ligneous tissue is charactensoc of xerophytes and so also are such modifica tions of tissue as the matted hairs, mineral waxy and varnish-like encrustations on the epidermis, the closing or concealing of SAO mata, etc.