216 PLANT ANATOMY. 
bundle* composed ? In the first place, it is necessary to.exclude 
therefrom any bast-cells (Fig. 133), which are, however, not at — 
all regularly united therewith even in the monocotyledons.* So 
long as it was not yet known that the bast-borders of the vas- 
cular bundles perform exclusively mechanical functions, they 
could be considered, and quite properly so, from purely anatomi- 
iv 
in) 
) 
ewe 
if 
> 
[) 
4, 
vy 
f 
i 
I 
I 
<a. 
Mf 
NYY. 
ii 
ITN 
A 
Hitt 
ia 
ii 
I 
Ws 
Whi 
) 
Mitt 
Tw 
ii 
Fig, 133. Fia. 134. 
Fig. 133.—Transverse section through a collateral bundle of the maize stem (monocoty- 
ledonous type). a, outer; i, inner; p, fundamental tissue; r, annular vessel: 8, spiral 
vessel; g, pitted vessel; 1, intercellular space (containing air); 2, wood-cells; v, phloém. 
The entire bundle is surrounded by a sheath of bast-cells (Sachs). 
Fic. 134.—Spirals capable of uncoiling and annular vessel from Bulbus Scille (longi- 
tudinal section), 
cal reasons, as belonging to the latter. Since it is known, however, 
that all bast-cells only serve to impart firmness to the plant, 
' With regard to the structure of the vascular bundles, which can 
only be briefly mentioned here, compare De Bary, ‘‘ Anatomie,” p. 328 
et seq. i ; 
* The bast border of the cribrose or sieve portion has been termed bast, 
that of the vascular portion, libriform. Compare the table on page 217. 
