280 CONVOLVULUS SOLDANELLA. 



have a multitude of snake-like stems issuing from the 

 expanded crown of their roots. In others the root itself 

 forms the reservoir, being as large as a turnip or a beet ; 

 while an annual vegetation of soft leaves and flower- 

 stalks is all that rises above the surface of the ground. 

 All these varieties of habit are obviously designed to 

 enable these plants to endure the climate and soil for 

 which they are destined. Nourishment in some is stored 

 up in the leaves, in others in the stem, and in others in 

 the root, that they may have something to feed upon 

 through the burning days and dewless nights of an 

 African summer. Other plants contend with the diffi- 

 culties of their situation by other means. Thus, one of 

 the most beautiful of our native sand-hill plants, Con- 

 volvulus Soldanella, sends creeping stems under the sur- 

 face of the sand in all directions, and these emit from 

 the joints, or nodes, bundles of finely-divided, hair-like 

 roots, that penetrate the loose soil, and ramifying as 

 they go along, are constantly forming mouths ready to 

 suck up every drop of water that penetrates the sand. 

 Besides this provision of abundant roots, its leaves, 

 though less fleshy than in some plants, are so in some 

 degree, and retain, in their tissues, moisture even in 

 seasons of drought. Along the sandy shores of other 

 countries, and throughout the tropics, are found species 

 of Convolvulus related to our G. Soldanella, and these 

 support existence by means of a similar system of creep- 

 ing underground stems and fibrous roots. But with 

 the soil the habit is varied ; thus, in the arid plains 

 of Persia, where probably a stiffer soil may prevent the 

 spreading of underground stems, there are species of 



