STRtrCTURE 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 



11 r^tMA'fti. 



m m 



Fig. 63. Fro. 64. Feb. 65. 



Fig. 63. — Part of a Sieve-Tube from Linden. 

 8, sieve-plates on tlie cell-wall, (x about 900.) 



Fig. 64. — Farts of Sieve-Tubes as found in Plants of tbe Gourd Family. 

 (Greatly magnified.) 



i, «, a sieve-plate seen edgewise ; above it a similar one, surface view. 



Fig. 65. — Cross-Section of Fir Wood. 

 8, a resin passage ; m, medullary rays. (Much magnified.) 



