



101 MKBISTEM TISSUE. 



11. The Raphides or Needle-shaped Crystals, in black bun- 

 dles in many cells of the Cortex, and in this tissue only. 



To a fi-esh section apply the tests for Crystals given on p. 3. 



In the Cross- Section: (Fig. 17.) 



OBSERVE: 1. The Epidermis, and outer zone of two or three 

 layers of cells ; form of latter. 



2. The zone of the Cortex cells, with frequent small intercell- 

 ular spaces. (See obs. 10 above). 



3. The Endodermis layer of the Cortex with a dark spot on 

 the common wall between. adjoining cells, due to a minute fold in 

 the wall. 



4. The Axial Cylinder. 



a. The Pericambial layer. 



b. The Bundles five to ten in number ; the Xylan mass (that 

 including the large duct openings) alternating with the thin-walled 

 Phloem, after the usual plan in roots. See Fig. of Acorns in Sachs' 

 Botany, p. 115; De Bary, pp. 10,348; Strasburger, p. 184; Good- 

 ale, pp. 105, 112; Vines' Text Book of Bot., p. 147. 



Make a sketch of a cross-section and the longitudinal section, 

 showing the zones and layers above mentioned. Also an enlarged 

 drawing of two xylem rays, the intermediate Phloem, Pericambium, 

 and Endodermal layers. 



A comparison should be made with the roots of a Dicotyledon 

 (Radish, Pea, etc.), treated after the same manner as directed above. 



With reference to the development of the various parts of the 

 root from distinct initial groups, several types have been described 

 by Janczewski, ' Flahault, and others.* See Goodale, p. 107; De- 

 Bary, p. 7. 



Type A. 



A SINGLE APICAL OR INITIAL CELL. 



Illustration : Root of FERN (Pteris) or EQUISETUM. 



PREPARATION: The same as for the previous study, except 

 that serial logitudinal sections mast be made in order to insure tin- 

 presence of the desired parts. See p. 35. In the median section, 

 OBSERVE : 1. The cone-shaped root cap covering the tip of the 

 root, not unlike the one in type B. 



2. Just beneath the cap and at the center of the root, the 



