14 Wilson—Observations on 
MATURE FLOWERING SHOOTS. 
A cross section, through any part of the flowering shoot 
above the tubercle, shows the following structure : 
(z) An epidermis made up of rather thick-walled cells, filled 
with a yellowish-brown protoplasm. 
(2) Parenchyma, made up of cells of varying size and thick- 
ness. The intercellular spaces are large and frequent. 
(c) Two concentric rows of separated collateral fibro-vascu- 
lar bundles. 
All of these points may be seen in Plate V, Figs. 1 and 3, and 
are not particularly noteworthy, although the double row of 
separate bundles is rather uncommon. 
Figures 2 and 3 on Plate V show the very remarkable 
relation of these bundles. Each bundle of the inner row has 
internally xylem, made up of xylem cells and well-developed 
spiral trachea. Next to the xylem is found the phloem, 
which a longitudinal section proves to consist of both sieve 
tubes and companion cells. Adjacent to the phloem are a 
number of parenchyma cells, whose walls are so angular and 
so much thickened, that in the photograph, these bundles 
appear to be bi-collateral. That such is not the case, how- 
ever, is easily proved on longitudinal section, when the paren- 
chymatous nature of these cells is at once visible. Even in 
cross section, the color of the walls differentiates the wood 
from the thickened parenchyma. 
The bundles of the exterior row have the same structure as 
those of the interior, only the xylem is now exterior so that 
the phloem masses of the two rows face each other. 
Plate V, Fig. 4, shows a photomicrograph of one of the 
exterior bundles. The wood is shown above, then comes the 
phloem, flanked below by the thickened parenchyma. On 
either side are the parenchyma cells characteristic of the 
major part of the flower stalk. The intercellular spaces are 
quite noticeable. 
