34 THE AMERICAN BOTANIST 



find this exemplified in the xerophytes or drouth plants which 

 for ages have been taught in the hard school of experience to 

 husban'd by all the means in their power the small amount of 

 water which they may suck up in their arid habitats. Among 

 them we find the most attractive and interesting of plant forms. 



In many regions, one may find representatives of all three 

 groups. If any are lacking it is likely to be the xerophytes for 

 these are true desert plants. It is not necessary, however, to 

 have a desert, in order to find examples. A ledge of dry ex- 

 posed rocks will furnish conditions quite comparable to those 

 of the 'desert and prove inhospitable enough to the few mosses, 

 lichens and annuals that may endeaveor to maintain life upon 

 them. A region of sand dunes, is also one of the best in which 

 to study the xerophytes. A number of the typically desert 

 plants are, of course, lacking, but the remainder are still so 

 characteristically drouth-plants that it is not difficult to look 

 at them and imagine a real desert. The sand dune region is 

 interesting, too from another cause. Usually between the hills 

 of sand are held small depressions containing water in which 

 a typically hydrophytic flora abounds, and we thus have the 

 two extremes of vegetation side by side with few if any of the 

 intermediate plants. 



An interesting feature of a sand-barren floras is the dis- 

 tinction that the soil makes between the so-called "calci- 

 philes" or lime-loving plants and the "calcifuges" or 

 those that do not grow well in calcareous soils. It is a dii^cult 

 matter to find representatives of the great heath family in 

 lime-stone regions, and a still more difficult matter to make 

 imported heathworts thrive in such soils. It is from this 

 cause that one cannot have thrifty rhodendrons in some lo- 

 calities. The absence of sphagnum bogs and their replacement 

 by sloughs and swamps is also influenced by calcarous matter 

 in soil water. But in sandy and clayey regions the heaths 



