yee 
2 
4 - , +s 2 rw ‘iy ha e » 
ae ce OO NO ek 
We ae th 2) eae Napigen’ Bing © ies fad 
Wen Paws metic A ~ b e Ga) Eo 
‘ el ea “ ; 
Die hn Shrised 
368 Structural and Physiological Botany. 
The prosenchymatous cells of the bast, which are also 
called bast-tubes, bast-fibres, or bast-cells, are asa rule fusiform — 
and unbranched. Septated bast-cells, similar to the sep- ci 
: tated wood-cells (p. 366), — 
are less common than the 
latter, but occur an eseie 
grape-vine and _ cactus. 
When young the bast-cells © 
contain a protoplasmic sap, 
at a later period usually 
air. In the Asclepiadeze 
and Apocynacee they con- 
tain a peculiar greenish sap 
related to the latex of other 
' plants. _ The bast-paren- 
chyma agrees almost en- 
tirely in its development 
and structure with the 
xylem. The vessels of the 
bast are sieve-tubes or lati- 
ciferous vessels. 
The presence or ab- 
sence, and the arrangement, 
of the separate elements in 
the cortex, are so~charac- 
teristic of most stems that 
they can be determined 
from these’ chatacters ia 
general idea may be ob- 
BiG fat «hart of f tanwverse section tained (by a itansv=nseaaae 
tuca scariola; Bf bast fibres; Bd bast tion through a bast-bundle 
parenchyma; mM” outer, m’ inner laticifer- 
ous vessels; Rf cortical parenchyma; HJ’ Of the wild lettuce (Fig. 
wood-fibres (x 400). 
an 476). | 
In woody Dicotyledons the pith {and the parts of the _ 
cortex which do not belong to the vascular bundles are very pe 
inconsiderable in comparison with these latter. The pith of 
