48 



MOEPHOLOGT OF STEMS AND BRANCHES. [tBSSON 6. 



for very dry regions ; and in such only are they found. Similarly, 

 bulbous and corm-bearing plants, and the like, are examples of a 

 •form of vegetation which in the growing season may expand a large 

 surface to the air and light, while during the period of rest the 

 living vegetable is reduced to a globe, or solid form of the least 

 possible surface ; and this is protected by its outer coats of dead 

 and dry scales, as well as by its situation under ground. Such 

 plants exhibit another and very similar adaptation to a season of 

 drought. And they mainly belong to countries (such as Southern 

 Africa, and parts of the interior of Oregon and California) which 

 have a long hot season during which little or no rain falls, when, 

 their stalks and foliage above and their roots beneath being early cut 

 off by drought, the plants rest securely in their compact bulbs, filled 

 with nourishment, and retaining their moisture with great tenacity, 

 until the rainy season comes round. Then they shoot forth leaves 

 and flowers with wonderful rapidity, and what was perhaps a desert 

 of arid sand becomes green with foliage and gay with blossoms, 

 almost in a day. This will be more perfectly understood when the 

 nature and use of fohage have been more fully considered. (Fig. 76 

 represents several forms of Cactus vegetation.) 



