Julia T. Emerson and William H. Welker 341 



and without the green. The substance of the "root " is much the 

 same throughout; firm, fibrous near the stem or a bud, more dif- 

 ficult to cut and tougher than a potato, and of a light yellow color. 

 Its general shape is round, like a gourd, A\4th a neck leadingup to 

 the shoots and several thick roots extending downwards, and it 

 may become as large as two feet in diameter and weigh many 

 pounds. There is a characteristic odor somewhat like that of an 

 earthy potato, and after working with fresh material some time 

 the nose and throat feel dry and irritated, while a bitter tasting 

 substance remains on the fingers, even after several washings. 



Figs. A and B show the organographic characters of the species, both at 

 the adult stage in its native habitat, and as a seedUng from four to five 

 years old. The large projecting root of Ibervillca in the specimens in the 

 greenhouses of the Botanical Garden reaches a diameter of from 25 to 30 

 cm. In the desert this enormous tuberous growth lying in the dry sand 

 looks like a gray, dust-covered boulder. Frequently irregularities of 

 shape give it still more the effect of stone, and it is only when the cortex 

 is flecked off that one discovers the healthy green color beneath the super- 

 ficial layer. From the tubers arise yearly long flexible liana-like shoots 

 which reach a length of three or more meters. The shoots are round, 

 smooth and green above, brown-gray and gray-spotted or streaked below. 

 The flowers are dioecious, the tendrils branched, and the leaves bright- 

 green and twice three-cleft as is so frequently the case throughout the 

 family. The fruit is said to be "amber colored" and 1} to li inch long; 

 none has ripened in the greenhouse, as the flowers there are staminate 

 only. The plant is able to persist in its arid habitat with remarkable 

 vitality. In fact, so provident is it of water and nutritive substances 

 that one in the museum case at the Garden which has been lying on a 

 board since 1902 is, in 1908, still sending up yearly shoots bearing leaves 

 and tendrils. Every fall the shoots die back and sprout again early the 

 next spring.' 



IV. GENERAL QUANTITATIVE COMPOSITION. 



Water, solids, organic and inorganic matter in the stem were 

 determined by the usual methods. After removal of the bark, 

 fresh portions of the stem- were quickly cut into small pieces and 



* Knox : Loc. cit. This paper gives the results of a thorough anatomical 

 study of the stem ("root") oi Ibervillea SonorcB. 



2 This tuber is ordinarily referred to as a root * * * xhe picture of 

 the old plant (Fig. A) with its shoots rising from the tuber, shows the 

 gradual enlargement of the stem, though the appearance of the seedling 



