PHYTOGENESIS. 245 
Spiral faserzellen, &c., pp. 7, 8) is based upon inaccurate ob- 
servation. 
These cells are at first generally filled with starch; rarely 
with mucus or gum. ‘The starch always passes into the latter 
substance in the progress of development; and this is con- 
verted into jelly, the change, as it would seem, taking place 
from without inwards. This jelly finally is converted at its 
outer surface into vegetable fibre, following the direction of a 
spiral lime, the coils of which are sometimes narrower, some- 
times wider. When these forms are observed in their different 
stages of development and in their various conditions, the idea 
involuntarily forces itself upon the mind that the spiral forma- 
tion is the result of a spiral movement of a fluid on the walls 
of cells between them and the central jelly. Horkel once 
actually observed the motion of small globules between the 
coils of the fibre in progress of formation in Hydrocharis. 
The great variety in the appearance of the fibres seems to 
depend upon the period of their origin, and on modification in 
the chemical changes of the formative material. It probably 
depends solely upon the former circumstance whether the spiral 
fibre lies free in the cell, when it is formed very late, or 
whether it is blended with the membrane of the cell, if its 
development commence at a period when the cell-membrane > 
itself is yet very soft and gelatious, and may consequently 
become agglutinated to the fibre, which is likewise still in a 
gelatinous state.’ This is the case in Casuarina, Cassytha, 
Hydrocharis, Trichocline, Orchis, &c.; in most cases, however, 
the cell-wall is too far developed to unite with the fibre, 
and the latter then les loose in the interior of the cell. In 
rarer instances the material is almost entirely applied to the 
formation of the fibre (always indeed when the fibre coalesces 
with the wall), for example, in Salvia Spielmanni, Mo- 
mordica elaterium. I have reason to suppose that this com- 
plete consumption almost always takes place in spiral vessels, 
and is the cause of their subsequently conveying only air. 
More frequently, however, one or more fibres are formed ; but 
then a great portion of the jelly has still remained uncon- 
' Subsequent researches have produced important modifications in this opinion. 
Consult my essay on the Spiral Formations in Vegetable Cells. Flora, 1839, Nos 
P22 slave 
