ON EAPHIDES. 
577 
within a delicate^ soft^ pale^ oval or oblong cell_, which they 
seldom completely fill^ being more frequently shorter than it. 
They are for the most part so loosely connected together in the 
bundle^ that their movements on or displacements from each 
other are as free as needles in a packet ; and they are apt to 
escape_, under gentle pressure^ from the cell during their 
examination. Each raphis gradually tapers or vanishes to a 
point at both ends^ and commonly presents no faces or angles 
when viewed with the aid of a low magnifying » power ; for 
whatever angles a raphis might have if formed separately 
these may be more or less checked or lost from the effects of 
attrition. The raphides of the bundle are also loosely con- 
tained within their cell^ which is commonly larger in its inside 
than the bundle of raphides^ sometimes twice or even thrice 
the size of that bundle_, and generally larger than the neigh- 
bouring tissue-cells. Occasionally the raphides escape regu- 
larly^ under the slightest manipulation^ from either end of the 
cell; these are sometimes distinguished as biforines. Raphides 
vary much in size in the same plant_, and more in different 
species and orders. In the following measurements^, all vulgar 
fractions of an English inch^ only average sizes are expressed^ 
and L. stands for length_, t. for thickness. Raphides of 
Imjyatiens, l. t. ^ ^ ^ q q ; of (Enothera and Epiluhiiimy 
L. T. T2 - o" o~o ^ of Galium and Crucianella, L. t. 
of Tamus, l. t. 5-0V0; of Tlrginea, l. t. YaVo- 
to them composition, in Epilohium, Galium, and officinal 
Sarza, it appears to be phosphate of lime ; in Mesem- 
hryanthemum and Eeliconia, oxalate of Hme and magnesia; 
in Veratnim, Richardia, and Golocasia, oxalate of lime.* 
Cr^^stal prisms are also acicular forms, but seldom occur 
more than two, three, or four in contact, and then closely 
side by side, as if partly fused together ; they are more often 
strewed singly throughout the plant-tissue ; and sometimes, as 
in the bulb-scales of the Shallot, they form crosses. The very 
same magnifying power under which the crystal prisms are 
plainly seen to possess three or four faces and angles will fail 
to show any such angles or faces on a raphis. Hor do the 
crystal prisms gradually taper at the ends to points, like a 
raphis, but their tips are either pyramids with the base corre- 
sponding to the shaft, or like a carpenteffs chisel, or wedge- 
shaped, or cut off’ obliquely from angle to angle or from 
face to face ; or the ends may be truncate, an appearance 
often caused by fracture. These crystals, when they lie in 
contact, are not easily separable from each other, nor from 
See the details of Dr. Davy’s examinations, and a notice of Dr. Macla- 
gan’s, in the Annals of Natural History^ June, 1864, p. 508. 
