192. Mr F. Cohn on the Contractile Filaments in Thisiles. 
ened, so that after about an hour they are shortened by 
about one-half. | 
Other means of death—as soaking in alcohol, glycerine, 
or even water—produce a like result; showing that shrink- 
ing by evaporation cannot be the cause of the shortening. 
By death the filaments are contracted to their minimum 
length. The ultimate projection of the style to about 
5 millimeters beyond the anther-tube depends mainly upon 
the shortening of the filaments in aye By this shorten- 
ing, the anther-tube is at last about S—1 millimeter below 
the corolla-points; while a few haan before it extended 
3-4 millimeters beyond them. 
The filament consists of a central bundle of annular and 
closely-wound spiral vessels, surrounded by longitudinal rows 
of long cylindrical cells with straight partition walls. Hx- 
ternally it is covered by an epidermis of similarly shaped 
cells, but which are more thickened and convex on their 
free surface, so that the filament appears uniformly chan- 
nelled. From the surface project peculiar conical hairs, 
each consisting of two flat cells applied to one another; 
these, as well as the epidermis cells, are covered by a pretty 
thick cuticula. When the contractile filament is elongated, 
the inner cells, seen in longitudinal section or otherwise, 
appear longitudinally striated, ‘‘as if they were provided 
with longitudinal fibres.” 
The contracted state of the cells is best seen when the 
anther-tube has come to be below the level of the corolla- 
points. By this time the cells of the filaments are all dead, 
as is proved by the shrunken primordial utricles, The cells 
are now all closely cross-striped—to appearance, as if the 
filament consisted of a number of spiral vessels. In those 
places where especially shorter cells occur, there is the 
closest transverse striation—almost like that of striped mus- 
cular fibre, This striation is caused by a very regular and 
close transverse corrugation of the cells, in the contraction 
of the filament; hence the side-walls of the cells appear 
finely and closely wrinkled, so that 10-20 cross folds occur 
in every 33, ofa millimeter. This corrugation affects all the 
cells,—including those of the epidermis,—except some in 
the centre near the air canals, whose cells often remain 
