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others, a healthy specimen of Kichardia gethiopica, which was kept 

 well supplied with water. It was soon perceived that the dripping 

 from the apex of the leaf had commenced, and it continued as long as 

 the weather was warm. 



On experimenting on this plant it was found that the greatest num- 

 ber of drops in a given time were to be obtained soon after the sun 

 had ceased to shine on the plant, which was at mid-day ; the number 

 never exceeded one in a minute, and generally they were not so fre- 

 quent as this. I was anxious to collect some of the fluid in order to 

 analyze it, and suspended a small vessel near to the apex ; during 

 the day and night I could thus obtain two or three drams from one 

 leaf. It was perfectly bright in colour and tasteless, and on apply- 

 ing tests which usually exhibit impurities in water no reaction could 

 be obtained. The plant was sometimes watered with a decoction of 

 logwood, yet no indication of its presence could be detected in the 

 colour of the fluid, or by the salts of iron ; in fact it appeared to be 

 pure water, notwithstanding that lime and other matters must have 

 been present in the water applied to the roots. 



Reflecting on the purity of the fluid, and how the plant could so 

 effectually separate the soluble impurities from the water absorbed, I 

 was at a loss to conceive how such a quantity could escape from the 

 minute apex, which it always did, and not from sundry other spots 

 then trickling towards the point, previous to its falling from the leaf 



As the escape of this fluid does not often occur when the plant is 

 out of doors, or if the sun shines on it when confined under glass, it 

 was imagined that under either of these conditions the evaporation 

 from the surface of the plant might be sufficient to carry off" any ex- 

 cess of water sent by the roots into the interior, under the stimulus of 

 increased temperature ; and that when evaporation could not so pro- 

 ceed, the channels which conveyed the fluid became surcharged, and 

 the apex, which seems as it were the confluence of numerous minute 

 streams, gives exit to the excess collected on account of suppressed 

 evaporation. 



It became necessary to apply to the anatomy of the leaf in order to 

 account for and prove the escape of the fluid from the apex. The 

 leaves of this plant are arrow-shaped, and terminated by a nearly cy- 

 lindrical point, varying fi'om half an inch to three quarters in length, 

 and about the twentieth part of an inch in diameter. The venation 

 makes one of the exceptions to the general rule, that the leaves of all 

 Endogens are straightly veined, for in this leaf is to be noticed an 

 arrangement of veins somewhat analogous to that of an Exogenous 



