GENERAL BIOLOGY 



2. Study a longitudinal section through part of an internode 

 and mount in water and study under microscope. Working from 

 the central cavity note the following: 



a. Pith cells. 



b. Fibro -vascular bundles, each containing (i) Spiral vessels, 

 (2) Wood cells, (3) Pitted vessels, (4) Cambium zone, (5) Bast- 

 cells, (6) Bast-vessels, large elongated cells with oblique per- 

 forated septa (sieve tubes), (7) Bast fibers. 



c. Cortex cells. . 



d. Epidermis with occasional stomata. 

 Drazv section. 



3. Study longitudinal section through a node and compare 

 it with that through the internode. Observe the bundles passing out 

 from the stem into the leaf. Draw. 



(II.) The Leaves. 



1. In prepared sections of a leaf observe the following parts: 



a. Colorless epidermis, with occasional stomata on upper and 

 lower surfaces. 



b. Mesophyll consisting of (i) Palisade cells, perpendicular to 

 surface and containing chlorophyll; (2) Spongy parenchyma, 

 composed of irregular branched cells containing chlorophyll, and 

 forming the lower half of the leaf substance. 



c. Intercellular spaces through the whole mesophyll com- 

 municating with the exterior through the stomata. 



d. Here and there sections of veins. Make out in them the same 

 parts as in the fibre-vascular bundles. 



Draw the section. 



2. Peel off a strip of epidermis from a leaf, mount in water and 

 examine under microscope. Observe : 



a. The large epidermal cells with wavy margins and no chloro- 

 phyll and occasional hairs. 



b. Here and there the stomata with two curved guard cells. 

 containing chlorophyll, bounding each opening. 



Draw. 



3. Gently pull a mid rib (vein) in two across its long axis; 

 note the fine threads uniting the two broken ends ; cut them off 

 with sharp scissors, mount in water, and observe under microscope 

 that they are composed of partially unrolled spiral vessels. 



Draw one of these. 



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