94 KLKMK. \TAIl Y 



3. The orifice of the pit, consisting of two "acutely divfr</i<j 

 lamellae.'' 1 De Bary, p. 167 ; Sachs' Physiology, p. 137 ; Bessey, 

 p. 27. 



PREPARATION THIRD: (c), (d) and (e) Radial longitudinal sec- 

 tion of the stem of BEGONIA, BEAN, BANANA, or better the material 

 used in PREPARATION SECOND. In this preparation, 



OBSERVE: 1. Large thin walled ducts with thickened spiral 

 markings. 



2. At various places the spiral bands broken loose from the 

 wall of the duct. 



3. In portions of the preparation some ducts may appear in 

 longisection, in which case, the ends of the thickened bands may be 

 clearly seen. 



4. The steepness and direction of coils, also the number of 

 bands. 



5. Their branching at various places, often forming in some 

 vessels a reticulation. This is the origin of the reticulated ducts. 

 Excellent material for their illustration can also be found in the 

 Cucurbitaceae and Impatiens. 



6. Certain ducts with the broad openings, between the, reti- 

 culations, arranged one above the other in the form of a ladder 

 Scalariform Vessels. Care must be taken to prevent confusing 

 these with the pitted vessels which they closely resemble. De- 

 Barj, p. 158. 



PREPARATION FOURTH : (f ) Longisection of the stem of CORN. 

 Zea Mays. 



OBSERVE: 1. Lying next the large spiral vessels of the bun- 

 dles, certain ducts strengthened by transverse thickenings in the 

 walls in the form of rings, the Annular Vessels. It is to be 

 noted that these are but a modification of the spiral ducts. De- 

 Bary, p. 156; Strasburger, p. 90; Bessey, p. 82; Sachs' Text Book 

 of Bot., p. 114 ; Physiology, pp. 91, 136. 



A modified form of Annular Tracheae exists in the Trabecular 

 J)uct, which has its walls strengthened by transverse bars across 

 the cavity. Good illustrations of this can be found in the fibro- 

 vascular bundles of the Juniper leaf. Bastin, p. 163 ; De Bary, 

 p. 156. 



