186 



true, it may be that the same explanation direct relation to the dry conditions is 

 will cover the case of the red flush so con- evident from the fact that the same plant 

 spicuous in buds and young 1 leaves in often produces smaller leaves in dry con- 

 early spring. It must not be supposed ditions than in moist. One of the most 

 that the need of protection has developed striking features of an arid country is the 

 the coloring, but since it is developed it absence of large leaves. These reduced 

 may be of some such service to the plant, leaves are of various forms, such as the 

 Even the conditions which determine au- needle leaves of pines, or the thread-like 

 tumnal coloration have not been made leaves of certain sedges and grasses, or 

 out certainly. the narrow leaves with inrolled margins 



It is instructive to notice how differ- such as is common in many heath plants, 

 ently the so-called evergreens, as pines, The extreme of leaf reduction has been 

 spruces, etc., have answered the problem reached by the Cactus plants, whose 

 of protection against the cold of winter, leaves, so far as foliage is concerned, have 

 The evergreens, instead of dropping their disappeared entirely, and the leaf work is 

 leaves, have undertaken to protect them, done by the surface of the globular, cylin- 

 giving them a small surface and very drical, or flattened stems. A covering of 

 heavy walls. In this way protection has hairs is an effective sun screen, and it is 

 been secured at the expense of working very common to find plants of dry re- 

 power during the season of work. Re- gions characteristically hairy. In such 

 duced surface and thick walls are both regions it is to be observed also that 

 obstacles to leaf work. On the other dwarf growths prevail, so that the plant, 

 hand, the deciduous trees have devel- as a whole, does not present such an ex- 

 oped the working power of their leaves to posure to the drouth as in regions of 

 the greatest extent, giving them large greater moisture. One of the most prom- 

 surface exposure and comparatively deli- inent measures of protection in dry re- 

 cate walls. It is out of the question to gions is the organization of what are 

 protect such an amount of surface during known as water reservoirs. Nearly all 

 the winter, and hence the deciduous hab- plants of such regions have leaves which 

 it. The evergreens are saved the annual are known as fleshy, that is, they are 

 renewal of leaves, but lose in working thick and juicy, being reservoirs of stored 

 power ; the deciduous trees must renew up moisture which is doled out cautiously 

 their leaves annually, but gain greatly in according to the needs of the plant, with- 

 working power. out any wastefulness. 



To obtain the most striking instances The whole subject of plant protection 



of protection, however, one must exam- is an immense one, and the illustrations 



ine plants which belong to permanently given above are merely intended to sug- 



dry regions, such as may be found in the gest that there is such a subject, and to 



United States along the Mexican border, lead to some observation of the various 



or in the regions of tropical deserts. In schemes of protection which are to be 



the first place, it will be noticed that the seen plainly on every hand, 



plants in general produce smaller leaves John Merle Coulter, 

 than in other regions. That this holds a 



Nature is but a name for an effect 

 Whose cause is God. 



-Cowper, "The Task." 



