STRUCTURE OF THE STEM 93 
peculiar pits. These pits, when young, are shaped much 
like two perforated watch-glasses, placed against a piece 
of cardboard, with their concave sides toward each other 
Fic. 63. — Part of a Sieve-Tube from Linden. 
$, Sieve-plates on the cell-wall. (x about 900.) 
Fie. 64. — Parts of Sieve-Tubes as found in Plants of the Gourd Family. 
(Greatly magnified.) 
$, 8, a Sieve-plate seen edgewise ; above it a similar one, surface view. 
Fic. 65. — Cross-Section of Fir Wood. 
8, aresin passage ; m, medullary rays. (Much magnified.) 
