548 
APPENDIX. 
and while thus softened you scrape or remove some of the veins 
which figure its surface, it will be found that they are almost 
wholly spiral vessels, which are of rather minute dimensions. 
“ There is something else curious respecting this seed. On its 
surface are numerous projecting cells which have very thick 
parietes : these can be found'^ burst and their contents emitted ; 
in fact they look more like eggs of some minute insect, which 
however they are not, as I have examined seeds of unopened 
almonds, where they exist likewise : they appear to me to be 
analogous to the cells which exist on the seeds of Cobaea scandens, 
which Don describes as mealiness^ but which is, instead, a beautiful 
example of fibro-cellular tissue.” 
To this I may add, that in the seed of Soymida febrifuga there 
lies in the middle of the wing a thick stratum of fibro-cellular 
bodies, which would be regarded as spiral vessels if they were 
longer and more cylindrical ; but which seem to be a curious and 
distinct form of fibro-cellular tissue. 
Page 43. 
In addition to the remarks here made upon Raphides, I have the 
satisfaction to insert in this place the following interesting com- 
munication from Mr. Quekett, upon the same subject : — 
‘‘ General Appearance . — Raphides are most frequently observed 
under two forms, appearing in one instance as transparent acicular 
crystals, which are either distinct from each other or united into a 
compact fibrous bundle, and in the other instance as small bodies 
composed of many crystals which radiate from the same centre, 
thereby forming a more or less spherical mass. 
Besides these two usual kinds, there are other forms, but of 
more rare occurrence, some of which are observed of regular 
crystalline figure ; as the rhombohedron in some cells of Calla 
sethiopica, and bark of Cascarilla ; octohedron, according to Meyen, 
in the stem of Tradescantia virginica; the rectangular prism in 
Quillaja saponaria ; and oblique prisms, which occur with acicular 
crystals, in Scilla maritima : but still there are a few varieties which 
present an irregular crystalline figure, some of which can be 
observed also in Tradescantia virginica, and in the inner layers of 
the bark of the Lime tree, where they seem very thin and pointed 
at the extremities, appearing like slices cut longitudinally from the 
middle of a square prism, which may be imagined to possess a four- 
sided pyramid at each end. 
“ Form, — With respect to the form of the acicular RaphideSy 
