QuEKETT on the Raphides of Cactus emieayonus, 21 
Raphides were first noticed in Malpiglii in Opuntia, and 
were subsequently described by Jurine and Raspail. 
According to the latter observer the needle-shaped or aci- 
cular are composed of phosphate, and the stellate of oxalate 
of lime. There are others having lime as a basis, combined 
with tartaric, malic, or citric acid. These are easily de- 
stroyed by acetic acid ; they are also very soluble in many of 
the fluids employed in the conservation of objects : some of 
them are as large as the l-40th of an inch ; others are as small 
as the 1-1 000th. They occur in all parts of the plant — in the 
stem, bark, leaves, stipules, sepals, petals, fruit, root, and even 
in the pollen, with few exceptions. They are always situated 
in the interior of cells, and not, as has been stated by Raspail 
and others, in the intercellular passages.* 
Some of the containing cells become much elongated, but 
still the cell- wall can be readily traced. In some species of 
Aloe, as for instance Aloe verrucosa^ with the naked eye you 
will be able to discern small silky filaments. When these 
are magnified they are found to be bundles of the acicular form 
of raphides. In portions of the cuticle of the medicinal 
squill — Scilla maritima — several large cells may be observed, 
full of bundles of needle-shaped crystals. These cells, how- 
ever, do not lie in the same plane as the smaller ones belong- 
ing to the cuticle. In the cuticle of an onion every cell is 
occupied either by an octohedral or a prismatic crystal of 
oxalate of lime — in some specimens the octohedral form pre- 
dominates, but in others from the same plant, the crystals may 
be principally prismatic, and are arranged as if they were be- 
ginning to assume a stellate form. 
Those persons who are in the habit of examining urinary 
deposits must be familiar with the appearance of the crystals 
of oxalate of lime, and would readily recognise their close 
resemblance to those in the cells of the onion. 
Raphides of oxalate of lime are found in very great abund- 
ance in the medicinal rhubarb — the best specimens from 
Turkey containing as much as 35 per cent. ; those from the 
East Indies 25 ; and the English, or that sold in the streets 
by men dressed up as Turks, 10 per cent. 
Buyers of this drug generally judge of its quality by its 
grittiness, that is by the quantity of raphides it contains ; and 
this is a curious fact, as the crystalline matter cannot be of 
any beneficial importance in the action of the medicine, for the 
* As as exception I may state that, many years ago, I discovered them 
in the interior of the spiral vessels in the stem of the grape-vine ; hut 
with some botanists this would not be considered as an exceptional case, 
the vessels being regarded as elongated cells. 
