20 BULLETIN 474, U. S. DEPARTMENT OF AGRICULTURE. 
vessel is in contact with wood-parenchyma fibers, and in horizontal 
rows where it is in contact with pith rays, often giving the vessel 
« scalariform (ladder-like) appearance. ‘The majority of vessels 
contain reddish-brown tyloses. These masses occur at regular inter- 
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Fic. 4, A—a, a, Two segments of a vessel, and 6, wood-parenchyma fiber, both separated 
from tze wood of Swietenia mahagoni; c, shows complete absorption of the partition 
walls of each vessel segment; d, small bordered pits. Magnified about 100 diameters. 
Fic. 4, B—Wood fiber( separated) of Swietenia mahagoni, showing cross-partitions at a. 
Magnified about 100 diameters. 
vals (longitudinal section), and often appear as minute partition 
walls within the vessels. They stain very readily with hematoxylin 
and dissolve under-the action of Schultze’s maceration mixture and 
