ANATOMY OF TISSUES. 65 
already been described, and according to them we have spiral, 
ring, ladder-form, reticulated, or porous ducts. There is also 
another method of support used only in very large ducts, 
FIG. 32. 
Elements of red beech in macerated condition. a member of a large duct ; 6 member of 
a small one with ladder-formed markings of cross wall. ec tracheid with bordered 
pores showing only the slit-formed canals, owing to effect of maceration. d bast. 
e parenchyma. f medullary cells of narrow ray. x 300.—(Th. Hartig.) 
namely, an irregular network of interlacing threads (or beams as 
they are called in German) which grow out into the lumen of 
the cell or duct. 
