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 FIG. 492. Diagram of a cross section through 

 oil fVio rar4c the stem of a fern (Pteris): s, s, s, rings of fibro- 



vascular bundles ; I, I, plates of strengthening tissue, 



Clearly differentiated with a ring of fibrovascular bundles between them ; 

 - . . -, j i Ip, zone of strengthening fibers ; r, cortex ; e, 



conducting bundles epidermis. 



occur in the mosses, 



but they are of much simpler structure than in the pterido- 



phytes, consisting usually of a single central strand, and are 



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 sori (sing., sorus), or spore clus- 

 ters, and the fronds or pinnae bear- . 

 ing them are said to be fertile. Are 



493 



494 



FIGS. 493-494. Parts of 

 fertile pinnae : 493, of polypo- 

 dium, enlarged, showing the sori there differences of size, shape, 



without indusmm ; 494, of pellea, 



showing indusium formed by the etc., between the fertile and the 



sterile fronds of your specimen? 



between the fertile and the sterile pinnae? On what part 

 of the frond are the fertile pinnae 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 



