Ch. XIV] THE XEROPHYTES 569 



the moist season ; typified by Testudinaria (Fig. 382), and 

 other forms in South Africa. 



C. The Dry Habitats, and the Vegetation Forms 



CALLED XEROPHYTES. 



These are the habitats in which, optimum in other re- 

 spects, both air and soil are dry for the greater part of the 

 year. To some extent tropophytic vegetation is found in 

 such places, but characteristic vegetation forms also occur 

 which keep in the vegetative state (evergreen) throughout 

 the long dry season. Such true xerophytes are further dis- 

 tinguished by the permanent possession of transpiration- 

 reducing features, including close set leaves, thickened 

 epidermis, reduced size, verticality of tissues, and associated 

 characteristics (pages 69-70). These features, while useless 

 during the moist season, are then no detriment ; and these 

 plants are accustomed to make most of their growth at that 

 time. Xerophytic evergreens occur among the deciduous 

 tropophytes in our temperate region forests, really as immi- 

 grants from the north, where they form great forests. The 

 advantage of the evergreen habit in such cases consists 

 in the longer season of activity, including even mild parts 

 of the winter, thus permitted. The principal xerophytic 

 vegetation forms are the following. 



Evergreen Excurrent Trees ; cone-shaped, with hori- 

 zontal branches and linear leaves, fitted to dryness and snow- 

 fall (pages 63-4, 179), but able to endure for a time meso- 

 phytic conditions ; typified by the Pines, Spruces, and Firs 

 (Fig. 122). Their xerophytism, primarily fitted to the phys- 

 iological dryness of winter, enables them to occupy physically 

 dry situations, like mountain slopes and gravel ridges. 

 Evergreen Excurrent Shrubs ; in principle like the fore- 

 going, but living in places where conditions prohibit trees. 

 Evergreen Broadleaf Shrubs; deliquescent, but with 

 leathery, thick-epidermed leaves; in forests, typified by 

 Mountain Laurel and Rhododendron. In regions of pre- 



