EXPLANATION OF THE ILLUSTRATION 
Prare LXATV. Sections of the secondary xylem of Medullosa Olseniae. 
Mig. 1. ‘Transverse section showing the outermost secondary xylem 
and the phloem of one of the “‘steles.** Note the radial rows of sieve 
elements (ight) and the flaring rays of the phloem (dark) in the up- 
per third of the figure. 20 
Nig. 2. Transverse section showing radial rows of tracheids separated 
by multiseriate rays of crushed cells. The lumena of the tracheids are 
black. 60 
Fig. 3, Same section shown in fie. 2, but more highly magnified. Note 
the multiseriate rays separating the double rows of alternately spaced 
tracheids, The black contents of the lumena are in sharp contrast to 
the bright layers of the inner tracheid wall and the pit chambers, the 
latter represented by bright beads. 115 
Fig. 4. ‘Vangential longitudinal section showing the long tylose filled 
tracheids and closely spaced crushed rays of the secondary xylem, 
20) 
hie, oO, Same section shown in fig. #, but more highly magnified. ‘Phe 
poor preservation of the rays is evident in the amorphous appearance 
of tissue between the tracheids. Note tyloses in the tracheids. bO 
hig. 6. Same section shown in fig. 4, but more highly magnified. The 
spherical structure in the center of the figure is a tylose which appar- 
ently developed within the pre-existing tylose of the tracheid. That 
the structure shown is organic and a part of the plant tissue is evident 
by the similarity in its optical properties with those of the surrounding 
cell wall residues. The upper wall of the primary tylose is represented 
by the rounded cell wall in the lumen of the tracheid in the upper 
part of the figure. = 260 
