Chai'. I] CHARACTERS OF TIIIC TKMPl'.RATl': CLIMATI". 423 



licibaccous, and to a certain extent quite essential constituents of grass- 

 hind, of desert, and of the herbaceous flora clothing the soil of woodland. 

 The importance of Gramiiieac is everywhere recognized ; Cypcraccac and 

 Juucaceac are widespread ; Liliaceae, Aviaryllidaccac, Iridaccac, and to a 



Fig. 234. Yucca .nrborescens in Ihe Mohave desert, California. After Coville. 



less extent Orchidaccac, are important constituents of the dry districts in 

 the warm temperate belts : in the hotter parts of extra-tropical America 

 Brovicliaceae possess a few \-er\- common species, for instance Tillandsia 

 usneoides, and in Chili species of Puya. 



