ior> MI-; i; IST KM TISSUE. 



In the middle longitudinal section of one of the bundles : 

 OBSERVE: 1. The Finl<ini<-ntul 7'fsaue (Parenchyma), on 

 the axial side of the bundle beyond its limits. 

 In the Axial Mass of Phloem: 



2. The Sieve- Tubes; known by the Sieve-like plates forming 

 the septa or occasionally seen on the lateral walls. See Sachs', p. 

 113 ; Bessey, p. 78. 



3. The Protoplasm enclosed in these tubes. 



4. The Fibrous-cells, fusiform in outline, scattered among the 

 Sieve-tubes or occurring in a band next the Spiral Ducts. 



In the Xyletn of the Bundle: 



OBSERVE: 5. The Spiral Ducts one narrow with a loose 

 spiral; another broader with a close spiral, occasionally becoming 

 reticulated. 



6. A Scalariform duct; see Bessey, p. 27, (Fig. 18 ;) some- 

 times this approaches (in this plant) a Pitted Vessel in structure. 



7. The Pitted Vessels very broad. 



a. The shallow pits on the walls in transverse rows showing 

 a "border" and "lumen." 



b. The ridges on the walls between rows of pits. 



c. The frequent occurrence of rings marking the partially 

 absorbed septa. 



8. The thin-walled cainbiform cells, with septa oblique or at 

 right angles to the lateral walls. This layer sepai'ates the A'////-/// 

 of the Bundle from the Phloem on the peripheral side of the 

 bundle. 



In these bundles it will be noted there exists a pi fnniin //f baud 

 of cambium, which insures the continued growth of the vascular 

 tissue. The bundle is therefore said to be an open one. 



Iu the closed bundles the procambium tissue becomes differ 

 entiated into permanent wood and bast, and the bundle undergoes 

 no further differentiation. The latter condition is the case in the 

 stems and roots of most Monocots, and Pteridophytes. Vines' 

 Text Book of Bot., p. 177. Strasburger, p. 83 ; Bessey, p. 121. 



In the I'< rifiln nil Muss of Phloem: 



9. Another group of S'i, >-, Tubes. 



10. A few Jlast Fibres. 



Trace in the cross section, the tissues, cells, etc., correspond- 



