DR. LANKESTER, ON RAPHIDES. 245 
ledge of the forms in which the soluble salts of plants exist 
is very limited; the recorded facts with regard to the salts 
which are insoluble are much more extensive; at the same 
time the number of those which have been observed is not 
large. 
The most common of the insoluble salts is undoubtedly the 
oxalate of lime. Schleiden says it appears to be present in 
every plant, but this is undoubtedly an error. The state- 
ment of Professor Gulliver with regard to the absence of 
raphides in certain plants contradicts this assertion; and 
what is very curious in his observations, is the fact that he 
has not been able to discover these erystals in the British 
Oxalidacez. The acidity of the Oxalis has been usually as- 
cribed to the presence of oxalic acid; and if this be true, it 
is certainly very strange and curious that the oxalate of lime 
should not be found in these plants. The oxalate of lime 
occurs in two principal forms. First, as large, single crys- 
tals, which are either elongated prisms, or octohedrons. 
They are frequently more or less rounded, or assume a dumb- 
bell form, arising from their crystallizing in contact with 
organic matters, as occurs with many other forms of crys- 
tals. Such rounded bodies are seen in the milky juices of 
plants, and have been regarded by Schultes and others as 
possessing vital properties of much importance in relation to 
the growth of the plant. Secondly, in the form of groups of 
crystals. In this form they are frequently developed upon an 
organic basis, and have been called by Meyen and others 
crystal glands. Itis to some of these compound crystals that 
Weddel applied the term Cystolithes. 
With regard to the form assumed by these crystals there 
has been some difference of opinion. Quekett took some 
pains to discover their exact form, and says, “That the four- 
sided is the ultimate form of these minute crystals is ren- 
dered more probable by the occurrence of rhombohedral and 
rhombic prisms, without pyramids of the same composition 
in the same plant, but of much greater widths; and there 
can be no doubt that these latter bodies and the acicular are 
two modifications of crystal of the same substance. The 
most decided proof of their being four-sided is obtained by 
pressing lightly on the piece of glass which covers them 
whilst examined under the microscope, when those which 
appear six-sided instantly appear four-sided, owing to the 
square crystal resting obliquely.” 
The acicular crystals, to which the name raphides have 
been more particularly applied, have been often described as 
having the same composition as the larger single and com- 
