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, 
WitiiaM Crark. 
XVII.—On the Watery Secretion of the Leaves and Stems of the 
Ice-plant (Mesembryanthemum crystallinum, Z.). By Dr. 
Aveustus VoELcKER, Prof. of Chemistry Royal Agricult. Col- 
lege, Cirencester *. 
A rew 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 ‘ 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 imorganic. 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 favourmg 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 flud. The secre- 
tion I procured by lacerating the gland-like eminences with 
* Read before the Botanical Society of Edinburgh, Jan. 10, 1850, 
