244: DR. LANKESTER, ON RAPHIDES. 
mon in some orders, it is remarkable that the raphides are 
so rare where they might be most expected, that I have not 
a single note of their presence in young parts of the stem, 
leaves, and flowers of British Oxalidacee, Umbellifere, 
Labiatez, Euphorbiacez, or Polygonacee, and even among 
Crassulacez. No crystals were found in Sedum Telephium 
and S. acre.” 
There can be no doubt of the important part that mineral 
substances play in the organization of both plants and 
animals, but the composition of these mineral matters, es- 
pecially in plants, is but imperfectly known. The method 
most relied upon for ascertaining their nature has been 
chemical analysis, but where this has been resorted to, after 
the destruction of the tissues of the plant by exposure to heat 
changes take place in the composition of the minerals, which 
render this method very uncertain. Fourcroy and Vauquelin, 
as long ago as 1809, showed that the greater part of the 
carbonates found in the ashes of plants were formed during 
the burning from other salts of vegetable acids. They proved 
that almost all plants contain acetate and malate of lime 
dissolved in the sap, also citrate, tartrate, and oxalate of lime, 
either dissolved or in a solid form, Certain elements are 
also expelled by heat, as chlorine, so that chemical analysis 
alone does not give us a satisfactory explanation of the com- 
position of mineral compounds in plants. The careful use 
of the microscope seems to offer a more satisfactory means of 
ascertaining really what the nature of these substances is. A 
large number of the salts present in plants are insoluble, and 
they present slender crystals in the tissues of plants, and it 
is these which have been observed by the microscope and 
called Raphides. Even with regard to the soluble salts, 
their forms might be made out by the evaporation of the 
juices in which they are contained, in the same way as has 
been so successfully pursued in making out the salts of the 
blood and urine. There can be no doubt that this subject 
affords an inviting field for research, and would amply repay 
investigation. The researches of Mr. Attfield on the nature 
of the efflorescence found on medicinal extracts show what 
may be done in this direction. The fact that so large a 
number of these crystalline productions are composed of 
chloride of potassium is very interesting, as pointing to the 
probability that the form in which potassium exists in land 
plants is really that of a chloride, and that the carbonates of 
potash obtained from the ashes of land plants are formed in 
the same way as the carbonates of soda from the sea plants, 
which contain chloride of sodium. The extent of our know- 
