my 
STRUCTURE OF THE STEM. 57 
oval figures, now show the whole length of the cell, and he 
may study the way in which they interlock at the ends. 
In the radial section the medullary rays will frequently look 
somewhat like portions of brickwork, as shown in Fig. 46. 
In the tangential section, only the 
cut-off edges of the medullary rays will Hl: 
be seen, as shown in Fig. 47. 
79. Separate Wood-Cells. — The com- 
plete outline of wood-cells and bast-cells 
is most easily made out by examining 
cells which have been separated from 
each other by soaking wood or bark, as 
the case may be, in a mixture of chlo- 
rate of potash and nitric acid until it 
can be easily picked to pieces in water 
and viewed under the microscope. In 
this way such cells as those shown in 
Fig. 48 may be isolated and studied. 
80. Ducts of Various Forms. — In 
most of the hard-woods the ducts are 
poorly shown in the longitudinal sec- 
tion, since they usually become much 
split and broken in the process of cut- 
ting the section. 
iJ 
rR = 
= es 
SE 
ati SS —_ 
ve,¢ es ry 
SA 
—y 
Fic. 47. — Longitudinal Sec- 
tion of Mahogany at right 
angles to the Medullary 
Rays, showing their cut- 
off ends.1 (Much magni- 
fied.) 
Study and sketch some of the following, as 
seen under a moderately high power : 
Radial longitudinal section of wood of tulip tree, longitudinal section 
of stem of bracken fern (Pteris), stem of castor-oil plant (Fig. 49), of 
peduncle of banana, or of root of chicory or licorice. 
81. Kinds of Tisswe.—The student has now become 
acquainted with a few of the many kinds of cells found in 
plants, and has begun to see how they are grouped together 
1The apparently vacant spaces at the ends of the lens-shaped sections of the 
medullary rays are in most woods filled with cells, like the rest of the section, 
