MacDougal — The Water -balance of Desert Plants . 93 
cornia annua , when the water-balance was low, and that absorption through 
immersed surfaces was exhibited by many plants . 1 
Purpose and adaptation may be easily read into such action. This 
kind of an interpretation seems forced, however, when it is considered that 
a capacity for absorption depends upon physical qualities, the primary 
significance of which relates wholly to other features of the activity of the 
plant. 
EXPLANATION OF PLATES VI-X. 
Illustrating Dr. MacDougal ’s paper on ‘ Water-balance 
Plate VI. Echinocactus Wislizeni , normal and cristate specimen below. Two plants of Carnegiea 
gigantea , the taller of which is about 150 years old. The smaller plant has been girdled by rabbits, 
and may survive many years in this condition. 
Plate VII. Echinocactus No. 4, with water-balance depleted by desiccation for 30 months. 
Plate VIII. Ibervillea sonorae, with old stem climbing on branches of Parkinsonia microphylla. 
Plate IX. A, Partial transverse section of stem of Dioscorea alata formed by desiccating tuber ; 
B, from normal stem of same ; C, tuber of Dioscorea alata with stems formed during desiccation. 
D, Brodiaea y with young corms formed during the desiccation. 
Plate X. Tubers of Ibervillea and Tumamoca y. fter desiccation for one year. Living and dead 
stems formed during this period are still attached. 
1 Transpiration and Behaviour of Stomata in Halophytes. Annals of Botany, vol. xxv, April, 
1911, p. 485. 
