MONOCOTYLEDONOUS 29 
are cross sections of vessels; surrounding these there will 
be seen cross sections of the fibers. Are the walls of the 
fibers thick? Note their cavities. The phloem is homolo- 
gous with the bark of the dicot stems. It consists of a 
group of light colored cells, situated nearly between the 
two most prominent vessels. Are these cells all of the 
same size and structure? The larger ones are sievetubes. 
The cambium region is found only in actively growing 
stems. It is situated between the xylem and phloem. 
Surrounding the entire bundie are several layers of small 
thick walled cells forming the bundle sheath. Select a 
bundle in which the structure can be clearly seen and 
make an outline drawing of it about 7 cm. in diameter. 
Represent the phloem in outline and draw all the larger 
vessels and a few cells of each of the different kinds of 
tissue found, including large and small phloem cells. 
Ask the instructor to criticise your drawing while you 
still have the sections under the microscope. 
Let the instructor give you some macerated fibro- 
vascular bundles and rind. Find isolated cells (fibers and 
several kinds of vessels) composing these tissues, com- 
pare them with their cross sections already studied, and 
describe them with regard to form as solids, thickness of 
cell walls, etc. How are they joined to each other? Draw 
two or three of each of the different kinds of cells. Judg- 
ing from what you now know about the different kinds 
of cells in a monocot stem, what do you think the func- 
tion of each kind is? Is their structure well adapted to 
their function? 
Literature. 
meevecrs: Introduction to (Bettany, 20.6 eek Soe oe ecw kk. 55-74 
