On the Secretion of the Leaves and Stems of the Ice-plant. 171 



necessary contributions from his stores in furtherance of such 

 objects, if undertaken under favourable auspices and competent 

 qualification ? 



I have opened a new field for exertion, particularly for the 

 younger naturalists, in which honour is to be acquired, and fur- 

 nished in the higher walks of observation, — a new theme, and I 

 trust that the " Hanc exorna" will be carried out with a zeal cor- 

 respondent to the importance of the subject. 



I am, Gentlemen, your most obedient servant, 



William Clark. 



XVII. — On the Watery Secretion of the Leaves and Stems of the 

 Ice-plant (Mesembryanthemum crystallinum, L.). By Dr. 

 Augustus Voelcker, Prof, of Chemistry Royal Agricult. Col- 

 lege, Cirencester*. 



A few months ago I had the pleasure of communicating to the 

 Botanical Society of Edinburgh the results of an examination of 

 the watery liquid in the ascidia of Nepenthes destillatoria. Those 

 present at the meeting, as well as the readers of the 4 Annals of 

 Natural History/ will remember that, in opposition to the state- 

 ments of most botanists who have directed their attention to the 

 subject of the watery secretions of the leaves of plants, I found 

 the liquid in the ascidia of Nepenthes to differ materially from 

 pure water, inasmuch as it contained from 0*30 to nearly 1 per 

 cent, of solid substances, partly organic partly inorganic. I 

 stated at that time my doubts as to the watery secretion of 

 plants being nothing but pure water, and gave some reasons for 

 this opinion ; Prof. Balfour, with whom I discussed the subject, 

 kindly furnished me with the means of investigating this point 

 still further by favouring me with fresh specimens of the curious 

 Ice-plant [Mesembryanthemum crystallinum), a plant which is re- 

 markable on account of the gland-like vesicular eminences with 

 which its leaves and stems are covered. The result of the examina- 

 tion of the fluid secreted by the leaves of this plant has fully con- 

 firmed the opinion expressed in regard to the watery secretions of 

 plants; at all events it has shown me that the secretion of the leaves 

 of the Ice-plant is not merely pure water, but water containing 

 several substances in solution. Though I was unable to determine 

 quantitatively the composition of this secretion on account of the 

 small quantity of liquid at my command — a quantity insufficient 

 even for a minute qualitative analysis — yet I had no difficulty 

 in detecting the chief constituent parts of the fluid. The secre- 

 tion I procured by lacerating the gland-like eminences with 



* Read before the Botanical Society of Edinburgh, Jan. 10, 1850. 



