LIFE HISTORY OF THE MALE FERN 



35 



B 



4. Fundamental tissue, resembling the last in aspect and function. 



5. Vascular Bundles. These are of two kinds, viz.: stem bundles 

 and leaf-trace bundles. Both are of elliptical outline, as seen in 

 cross section, and are embedded in the parenchyma forming the 

 broad central matrix. The stem bundles are comparatively broad 

 and, as viewed in longitudinal sections, form a continuous network 

 with good-sized meshes, each mesh being opposite the point of in- 

 sertion of one of the leaves (See Fig. 13). 



In transverse section these bundles are 

 seen to be usually ten in number and ar- 

 ranged in an interrupted circle within the 

 fundamental tissue. The leaf -trace bun- 

 dles are comparatively narrow and are 

 observed to come off of the stem-bundles 

 and pass out through the cortex into the 

 /leaves (fronds). When each bundle is 

 examined under a high-power magnifica- 

 tion it is seen to be composed of: (a) an 

 endodermis or bundle sheath, a single layer 

 of cells with yellowish walls and granular 

 contents; (o) a per^camb^um or phloem 



FlG - I ^~ A - Cylindrical 



network of vascular bundles 



i n the stem of Dryopteris 

 sheath of one to three layers of delicate Fiiix-mas. B. A portion of 



,, . n j n i i / \ the same more highly mag- 



thin- walled cells, rich in protoplasm; (c) a nified. At L are the inter- 

 phloem, a broad zone of tissue formed of stices over w hich the leaves 



,,...., are inserted; at G are 



phloem cells, with thin cellulose walls and branches (leaf trace bun- 

 protoplasmic contents, which convey sugar dles ) P assin s into the leaves 



. . p from the main vascular 



involution irom the leaves to the roots and bundles. (Sayre.) 

 broader sieve tubes which appear polygonal 



in transverse section and whose function is that of conveying soluble 

 proteins in the same direction; (d) a xylem (wood) formed of thin- 

 walled xylem cells which store food and scalariform tubes or tracheids 

 which conduct crude sap (water with mineral salts in solution) from 

 the roots to the leaves (fronds) . Since the xylem is surrounded by the 

 phloem, the fibre-vascular bundle is of the concentric type. Strictly 

 speaking the endodermis and pericambium are accessory regions, sur- 

 rounding, but not part of the bundle proper. 



