100 ANATOMY AND PHYSIOLOGY OF 



appeared at firbt like pare water, contained organic sub&tances, 

 and passed into foetid decomposition. Similai observations were 

 made by Eainer Graf (" Flora;' 1840, 433), ^ 



Wliile this excretion of water occurs only in very small amount 

 in most plants, manj;^ of the family of the Aroide^e, especially Galla 

 mthiopica (Gartner, ^^Beihlatter zut Flora" 1842, 1), Arura Colo- 

 c isia (Schmidt, in Limicea, vi. 65), evacuate water in larger quan- 

 tity from the points of their leaves, so that it flows off in diops ; 

 this occurs in the most striking degree in a plant described as 

 CaladiuTTi destillatorum (" Aom, of Nat Hist" sec, ser. i. 188), 

 in which each leaf — it is fcrue, of colossal size — gave off about half 

 a pint every night. The water flows here (as in Arum Golocasid) 

 from an orifice in the neighbouihood of the point of the leaf, upon 

 the upper surface, in which terminates a canal running along the 

 border of the leaf, while smaller canals, running along the prin- 

 cipal nerves, open into this. 



The water secreted, in all these cases, contains but an extremely 

 small quantity of organic substance in solution. 



It is probable that the secretion of water in the pitchers of 

 Nepenthes, Sarracenia, and Gephalotus, should be reckoned with 

 the above. According to Volcker s account (" Ann. of Nat Hist" 

 sec. ser, iv. 1 28), the fluid secreted by Nepenthes contains only 

 0,27 — 0,92 per cent, of solid matter, consisting of citric and malic 

 acids, chlorine, potash, soda, lime, and magnesia. 



We have no data which would enable us to determine accu- 

 rately how far this secretion of drops of fluid water is (as accord- 

 ing to Trinchinetti) for the purpose of evacuating substances, 

 which, if they remained in the plant, would exercibe an injurious 

 influence upon its health; yet this hypothesis hardly appears 

 probable, when we take into account the extraordinarily small 

 quantity of organic compounds removed in this way, together 

 with the circumstance that they bear none of the characters of a 

 substance beginning to sufler decomposition. 



The same holds good, also, in regard to the water excreted 

 from the leaves in the form of vapour. This likewise contains, as 

 the observations of Senebier and Treviranus shewed, an ex- 

 tremely small quantity of organic matter, but is nevertheless 

 capable of putrefaction. Experiments which were m ade by Bonnet, 

 Duhamel, and Treviranus {'' Phys!' i. 494), to hinder the evapora- 

 tion, by smearing the leaves with oil and other substances, shewed 

 that the leaves died. This result may, however, be just as well 

 attributed to a positive injurious effect of the oil, in withholding 

 PIT, as to a suppression of the evacuation of injurious matter. 

 Manifold experience puts it beyond doubt that repression of the 

 evaporation from the leaves by unfavourable conditions of weather, 

 produces disease, often connected with the formation of Fungi, but 

 this result may be caused quite as much by a disturbance of the 

 normal nutrient processes of the plant connected with the evapora- 



