84 ELEMENTARY TISSUES. 







plied with alcohol to prevent access of air. Mount in alcohol or 

 glycerin. 



OBSERVE 1. Epidermis of the upper and lower sides of the 

 leaf, appearing almost colorless as seen in section. 



2. The thickened (cutinized) outside walls of the cells, which 

 are in very close contact with each other. 



3. The palisade cells (ellipsoidal) , and the underlying layers 

 of irregular parenchyma cells making up the mesophyll of the 

 leaf. These cells form the main body of nearly all leaves. Note 

 the large irregular i)itercclh<l<tr .traces in connection with them, 

 also their contents in the sections of fresh tissue. 



4. Stomates in section over small intercellular spaces. 

 PREPARATION FIFTH: STELLATE PARENCHYMA from STEMS and 



PETIOLES of many aquatic plants. 



Liliaceve and Pontederiaeeve, furnish excellent material for this 

 study. 



Make several thin transections from the* stem or petiole of 

 PoMederia and mount in water. 



OBSERVE 1. The firm regular epidermal parenchyma with 

 slightly cutinized walls. 



2. The loose isodia metric cells making up the interior of the 

 section. 



3. Large air-passages occupying a considerable portion of the 

 section. 



4. Certain spaces filled with stellate cells, having their project- 

 ing ends in contact and forming a sieve-like plate across the cavity. 

 .(Fig 12.) 



The function of these plates is probably to form a support for 

 the cross running fibro- vascular bundles, and at the same time, allow 

 the free passage of air through the stem (Bot. Jahresbericht; I, I'.Ml.) 



5. The large nuclei and granular protoplasmic contents. 

 PREPARATION SIXTH: Suberous cells, from the "CoRK OAK," 



Quercus Suber, (commercial cork.) 



Mount several very thin sections in water; mount others in 

 alcohol on the same slide. Suberin, the peculiar substance of cork 

 cells, repels water, and the comparison between the two prepara- 

 tions should be made as soon as possible. 



