THE EXCRETION OE XECTAK 281 



minute, while from the leaf of Colocasia antiquorum Duchartre counted twenty-five 

 to twenty-six drops per minute, and collected from the latter plant 22-6 grams of 

 fluid in a single night '. Although as a general rule the drops collect slowly, in 

 Colocasia Musset noticed that they appeared suddenly, and might be thrown to 

 a distance of 10 centimetres, but Munting (1672) was probably exaggerating when 

 he stated that he had seen a fine stream of water, like a fountain, springing from 

 the leaves of Aroids ' 2 , although it is not impossible that such a result might be 

 produced if water were forced into the plant under strong pressure. At any rate 

 it is possible by such means to increase very considerably the rate at which water 

 is excreted, and so to drive large quantities of fluid through the plant in a 

 comparatively short time '. 



The fluid excreted from the water-stomata has been found to have a composi- 

 tion similar to the sap obtained from bleeding plants, except that it is more diluted 

 (Sect. 43), since it contains only o-ooi to 0-05 per cent, of dissolved substances 4 . 

 The fluid from the pitchers of Nepenthes is not quite so dilute, and contains, 

 according to Volcker, 0-85 to 092 per cent, of solids 5 . On the secretion of 

 enzymes, &c. by Nepenthes and other carnivorous plants, see Sect. 65. 



SECTION 49. The Excretion of Nectar. 



A nectary may be produced at any point where the cells can excrete 

 sugar, provided the cell-walls are permeable to water, and that the osmotic 

 action of the extracellular sugar is thus able to withdraw 

 water from them (Sects. 46, 47). An artificial nectary may be 

 formed by placing a little sugar in a hollow on the cut surface 

 of a beetroot or a potato, when water is extracted from the 

 tissues until the sugar all passes into solution, and so long as 

 the beetroot or potato contains plenty of water, the size of the 

 drop may remain constant in spite of continuous evaporation FlG 40 

 (Fig. 40, 11), or it may increase considerably in a saturated 

 atmosphere. Just as in ordinary plasmolysis, scarcely anything but water- 

 is withdrawn from the cell, so that when a beetroot is used for this experi- 

 ment, the sugar solution remains uncoloured so long as all the cells with 

 which it is in contact remain living. 



1 Musset, Compt. rend., 1865, T. Lxr, p. 683; Duchartre, I.e., p. .'50; Cornu, Compt. rend., 

 1897, T. cxxiv, p. 666. 



2 Reference in Flora, 1837, P- 7 1 ?- 



3 Sachs, Vorlesungen iiber Pflanzenphysiol., 1887, 2. Aurl., p. 259. 



4 Unger, Sitzungsb. d. Wien. Akad., 1858, Bd. xxvnr, p. 19; Duchartre, I.e., p. 241, and the 

 literature given by Burgerstein (Materialien, &c., 1889, n > P- 49) '> a ^ so Haberlandt, I.e., 1895, 

 p. 62 ; Volcker, quoted by Wunschmann, Uber die Gattung Nepenthes, 1872, p. 25. 



R [Koorders (Ann. d. Jard. hot. d. Buitenzorg, T. xiv, 1897, pp. 355, 449) finds that the fluid 

 present in the 'water-calyces' of many tropical flowers contains from 0-3 to 0-7 of solids, the greater 

 part of which usually consists of organic substances, probably chiefly sugar. The fluid may be acid 

 or alkaline, and is apparently intermediate in character between that excreted by hydathodes and 

 that by nectaries.] 



