22 CELLULAR TISSUE. 
These were supposed by M. Kieser, to be the principal chan- 
. nels through which the sap ascends. The ‘“ vital vessels,” 
or “ ducts of the latex” of M. Schultz, which are found in 
the bark near the surface, and anastomose (branch and join 
frequently), are considered by some to be intercellular canals. 
52. These intercellular passages are frequently distended, 
and form large cavities, filled with the peculiar secretions of 
the plant. These were formerly termed proper vessels, (vasa 
propria), from containing the proper juice. They are of 
various forms, round, cylindrical, &c. The term “ recepta- 
cles” is now frequently applied to them, as they contain the 
peculiar secretions, or detached fluids, as oils, belonging to — 
the plant. 
53. Some plants, particularly aquatics, present a regular — 
series of cells of a very large size, filled with air. These are 
termed air-cells, or lacune, and are supposed by some to be 
caused by rupture of the cellular tissue, by others, to be dis- 
tensions of the intercellular spaces. They assist in. elevat- 
ing”aquatics towards the surface of the water. = 
54. The contents of the cellular tissue are generally fluids. 
In many parts ¢hey contain small granules or globules, scat- 
tered through the liquid, which remain attached to the sides 
of the cell after the liquid has disappeared, and the cell 
dry. These globules are of a greenish colour, and along 
with green coloured fluid, are the source of the colour in 
the parts of a greenish hue. In other parts the colour seems 
to be entirely owing to the liquid the cells contain, as in the 
colours of flowers, the sides of the cells themselves being co- 
lourless. Granules found in the cellular tissue are regarded 
by Turpin and Raspail, as the source of the growth of cel- 
lular tissue—as young cellules—the seeds, as it were, of t 
future cells or vesicles. They are called globuline by Tur 
pin. They are supposed to constitute starch. 
55. Scattered through the cellular tissue, in 
lular passages, according to some, and in the 
ing to others, needle-shaped crystals are often 
Raphides. They are composed, some of | 
