44 Dr. M. J. Schleiden on Spiral Formations. 
layers of the oldest heart wood constantly exhibited more or 
less distinctly these delicate stripes, and the pores then again 
appear merely as narrow clefts between two separating spiral 
coils. 
In consequence of this view of mine of the constant gene- 
rality of the spiral arrangement of the secondary depositions, 
I am also inclined, for the sake of consistency, to deduce the 
reticulated figures on the cells of the liber of the Apocynee, 
of the parenchymatous cells of numerous tropical Orchidee, 
superposition Dahlia tubers, &c., rather from the adeumbency 
of two exceedingly delicate layers, formed of contrarily wound 
spirals, than to have recourse to quite a new mode of arrange- 
ment, which seems justified by no other peculiarity of the 
organ or of the occurrence. But I perceive it might be diffi- 
cult here to bring direct observation in aid. 
I may allow myself, in conclusion, some observations on’ 
the direction of the spiral coils. That all the reasons ad- 
vanced by Meyen and Link respecting the difficulty of the 
determination do not at all affect the subject, is evident; for. 
by reversion the relative position of two spirals is certainly 
not altered; but even the individual spirals remain wound 
right or left, in whatever way they are observed, of which 
Meyen may easily convince himself on a rod figured with a 
spiral. The being wound right or left of a spiral depends not 
merely on a different mode of viewing it, but on an internal 
difference in its mathematical construction. Moreover the 
sole actual difficulty mentioned by Mohl is not of such a 
nature that it cannot be overcome by a good microscope and 
some practice of the observer. In general I cannot agree 
with Mohl, that the spiral vessels principally occur wound to 
the right ; I found some left-wound very frequently, and differ-. 
ences in various individuals of the same species. From my 
observations up to the present time, I have provisionally abs- 
tracted the following rule as at least very frequently valid. 
“ Tn all spiral formations developing cotemporaneously, (com- 
prising in the most general meaning all secondary depositions,) 
those which are situated immediately on one another in the di- 
rection ‘of the radius are wound in the same direction; but 
those lying immediately on one another in the direction of the 
parallels to the periphery are wound in different directions. 
I will only mention here, as an instance, some spiroidea from 
Cucurbita Pepo ; and I moreover appeal to the constant cross- 
ing of the pore fissures in contiguous parenchymatous and 
ligneous cells when observed on sections parallel to the me- 
dullary rays. But I must at once name, as a considerable ex- 
ception, the peculiar short, thick, but delicate walled cells, 
