CRYPTOGAMS 347 
Make a longitudinal 
section of a rhizome 
through the point 
where a leafstalk is 
attached and trace the 
course of the bundles. 
This will be facilitated 
if the specimen has 
stood in eosin solution 
a few hours. Make 
enlarged drawings of 
both sections, labeling 
all the parts. 
Clearly differentiated 
conducting bundles 
occur in the mosses, 
Fic. 492.— Diagram of a cross section through 
the stem of a fern (Pteris): s, s, s, rings of fibro- 
vascular bundles; J, 1, plates of strengthening tissue, 
with a ring of fibrovascular bundles between them ; 
lp, zone of strengthening fibers; 7, cortex; ¢, 
epidermis. 
but they are of much simpler structure than in the pterido- 
phytes, consisting usually of a single central strand, and are 
493 
Fics. 493-494.— Parts of 
fertile pinne: 493, of polypo- 
dium, enlarged, showing the sori 
without indusium ; 494, of pellea, 
showing indusium formed by the 
revolute margin. 
found more frequently in the leaves 
than in the stems. A true vascular 
structure appears first in the pteri- 
dophytes, whence these plants are 
distinguished as vascular cryptogams. 
404. Fructification. —- Examine 
the back of a fruiting frond; what 
do you find there? These dots are 
the sort (sing., sorus), or spore clus- 
ters, and the fronds or pinne bear- 
ing them are said to be fertile. Are 
there any differences of size, shape, 
etc., between the fertile and the 
sterile fronds of your specimen? 
between the fertile and the sterile pinne? On what part 
of the frond are the fertile pinne borne? Notice the shape 
and position of the sori, and their relation to the veins, 
whether borne at the tips, in the forks, on the upper side 
