STRUCTURE OF THE STEM. 
61 
83. Stem of Conifers.1— Sketch the end of a cut-off billet of hard 
pine or red cedar. 
Study the cut surface with a magnifying glass and 
decide whether any of the parts readily found in the wood of the coarser- 
grained hard-woods are absent from coniferous wood. 
Under a power of 100 or more diameters it is easy to see what it is 
that marks off one annual ring from another. 
Study the section, compare it with 
Fig. 50, and state the difference between 
spring wood and fall wood. 
Sketch the whole 
moderately magnified 
Examine longitudinal sections, both 
radial and tangential, of pine, spruce, fir, 
or red cedar.? 
Sketch a radial section and a tangen- 
tial one, labeling the medullary rays and 
the cells of the wood, with their circular 
markings, as shown in Fig. 51. 
84. The Early History of the 
Stem. —In the earliest stages of 
the growth of the stem it consists 
entirely of thin-walled and rapidly 
dividing cells. Soon, however, the 
various kinds of tissue which are 
found in the full-grown stem begin 
to appear. 
In Fig. 52 the process is shown 
as it occurs in the castor bean. 
At m, in B, is the central column 
of pith, surrounded by eight fibro- 
vascular bundles, fv, each of which 
contains a number of ducts arranged 
cross - section, 
A 
Fie. 52.—Transverse Section 
through the Caulicle of the Castor- 
Oil Plant at Various Stages. 
A, after the root has just appeared 
outside the testa of the seed; B, 
after the caulicle is nearly an inch 
long; C, at the end of germina- 
tion; 7, cortex (undeveloped 
bark); m, pith; st, medullary 
rays; jv, fibro-vascular bundles ; 
cb, layer of tissue which is to 
develop into cambium. (Consider- 
ably magnified.) 
in a pretty regular manner and surrounded by the forerunners 
of the true wood-cells. 
1 That is, of the cone-bearing trees (mostly evergreens), such as the pines, spruces, 
cedars, larches, and so on. 
2 Pine shows the large circular pits very plainly, while red cedar shows the medul- 
lary rays most clearly, since nearly all its red color lies in these. 
