March 11, 1904.] 



SCIENCE. 



419 



second pitcher within the outer one; (3) 

 the shape of the outer pitcher, which is 

 broader than long, and (4) the growth of 

 the plant on dead bamboos instead of dead 

 trees, as with D. 7-a fflesiana. The presence 

 of a purple color on the under surface of 

 the pitcher the speaker believed to be cor- 

 related with the growth of the roots on that 

 side and is not, as Groom claims, to shade 

 the roots from too intense light. The ab- 

 sence of dead or partially digested ants 

 would exclude the possibility of the pitch- 

 ers being insect traps. In all probability 

 they serve as chambers where water in the 

 aqueous or gaseous state collects, and for 

 the collection of humus upon which this 

 asclepiadaceous plant primarily depends 

 for food. 



On the Excretion of Hygroscopic Salts in 



Frankenia and Statice: Mr. T. H. 



Kjiaeney, United States Department of 



Agriculture. 



Certain plants of arid regions, notably 

 members of the Tamaricacea, Frankenia- 

 cese and PlumbaginaccEe, have long been 

 known to possess the property of excreting 

 salts in solution by means of epidermal 

 glands of highly specialized structure. 

 The excreted salts, in the eases recorded, 

 are strongly hygroscopic. During the day- 

 time when evaporation is intense, they exist 

 as a dry granular deposit or as a thin con- 

 tinuous coating on the surface of the plant, 

 while during the night they take up water. 

 In the early morning the leaves and stems 

 are often covered with drops of solution. 



Observations were made upon Frankenia 

 grandifolia in California and Statice limo- 

 niu,m, var. Calif ornica in western Texas, 

 both plants occurring in moist, strongly 

 saline soils. In both cases chemical analy- 

 sis showed that the principal constituents 

 of the excretion were also the principal 

 soluble constituents of the soil in which the 

 plants were growing, although the propor- 



tions differed sufficiently to indicate select- 

 ive power on the part of the plant. In 

 Frankenia, sodium and hydrochloric acid 

 were the principal constituents of the ex- 

 cretion, while in Statice, calcium and sul- 

 phuric acid predominated. That the 

 glands function actively in the process of 

 excretion was demonstrated by brushing 

 over portions of the leaf surface in living 

 plants with an alcoholic solution of mer- 

 curic chloride. Areas thus treated nearly 

 or quite ceased to excrete, while unpoisoned 

 areas of the same leaf continued to excrete 

 vigorously. Hence the 'salt glands' evi- 

 dently belong to that type of hydathodes or 

 water-excreting organs in which an active 

 glandular function is involved. 



What is the significance to the plant of 

 this excretion of salts? Volkens, on the 

 basis of a simple experiment performed 

 upon Rea^irmma hirtella near Cairo, con- 

 cluded that the glands are able to take up 

 water from the strong salt solution with 

 which the surface of the plant is covered in 

 the night and early morning, and thus sup- 

 plement the roots as absorbing organs. 

 Marloth and Haberlandt, however, have 

 shown that Volkens 's experiment does not 

 necessarily prove more than a reduction of 

 transpiration effected by the presence of 

 the salt excretion. 



A series of experiments upon Statice by 

 the writer demonstrated that the absorbing 

 power of the uninjured surface of the liv- 

 ing leaves, even when immersed in pure 

 water, is very small. Furthermore, con- 

 centrated salt solutions, applied either by 

 immersing the leaf in them with the cut 

 surface protected from contact with the 

 solution or by placing a small amount of 

 powdered calcium chloride on leaves kept 

 in a saturated atmosphere, so far from giv- 

 ing up water to the leaves, actually with- 

 drew a large amount from them, although 

 not causing plasmolysis under these condi- 

 tions. Addition of coloring matter to salt 



