va 
CYSTOLITHS OR LITHOCYSTS. 35 
of Rumex (fig. 56); or in groups radiating from a common 
point, and then assuming a clustered or conglomerate appear- 
ance, as in the stem of the common Beet (fig. 55). The former 
have been termed acicular raphides, and the latter conglomerate 
raphides. 
In some interesting researches into the nature of raphides 
made several years since by Professor Gulliver, he has distin- 
guished the acicular crystals (fig. 56), which he called true 
raphides, from those which occur either singly (fig. 54), or in 
more or less globular or conglomerate masses (jig. 55), which he 
has termed Sphexraphides. He believes that the presence or 
absence of the former or true raphides, and their comparative 
abundance, afford characters by which the species of certain 
orders may be distinguished at once from the allied species of 
neighbouring orders. He has instanced the plants of the Ona- 
grace, especially, as being in this way readily distinguished 
from the plants of allied orders. Gulliver speaks very strongly 
upon this point as follows : ‘No other single diagnosis for the 
orders in question is so simple, fundamental, and universal as 
this; and the orders to which it applies should be named 
raphis-bearing or raphidiferous.’ 
With regard to Spheeraphides, Gulliver believes that there 
are few, if any, orders among Phanerogams in which they do 
not exist; hence it is questionable how far their distribution 
might be rendered available as a means of distinguishing plants 
from one another. ‘Their presence, however, he finds universal 
in every species of the orders Caryophyllaceze, Geraniacez, 
Paronychiacex, Lythracez, Saxifragaceze, and Urticacez ; hence 
he regards the presence of Spheraphides as especially charac- 
teristic of these orders. 
In the common Arum, where raphides are very abundant, 
and in some other Aracez, the cells which contain the raphides 
are filled with a thickened sap, so that when they are moistened 
with water endosmose take place, by which they are distended 
and caused ultimately to burst and discharge their crystals from 
an orifice at each end (fig. 57). Such cells were called Biforines 
by Turpin, who erroneously regarded, them as organs of a special 
nature. : 
In many plants belonging to the families of the Urticacee, 
Morace:e, and Acanthacez, there may be frequently observed 
just beneath the surfaces of the leaves, or sometimes more 
deeply situated, peculiar crystalline structures, to which the 
name of Cystoliths or Lithocysts has beenapplied. These consist 
of an enlarged cell containing commonly a globular (fig. 58), or 
somewhat club-shaped (jig. 59) mass of crystals, suspended from 
the top by a kind of stalk formed by an ingrowth of the cell-wall, 
upon which the crystals are deposited as upon a nucleus. 
Crystals of various composition have been described as 
occurring in different plants, but more accurate observations 
D2 
