MARCIfANTIA POLYMORPHA. 6 1 



a. A circular breathing-pore, or stoma, readily de- 

 tected with the lens. 1 



6. On the under surface, notice the absence of stomata 

 and areohi3. 



7. Make an outline sketch of a branching stem to show 

 the contour, the median line, and the mode of branch- 

 ing. 



8. Mount a transverse section, and if from a growing 

 plant, notice the pale middle tissue, the green upper 

 surface, the dark-colored lower surface, and the group 

 of median leaves projecting downward from the mid- 

 rib ; if from an alcoholic specimen the color is wanting. 

 If the specimen is very thin and carefully prepared, 

 long narrow air-cavities may be seen just beneath the 

 upper surface with possibly stomata leading out from the 

 center of some. 



C. THE LEAF. Remove the hairs from the lower sur- 

 face of the stem, and notice 



1. The direction and manner of the overlapping of the 



leaves. 



2. The shape. 



3. The curvature and extent of the line of insertion. 



4. Illustrate shape, and position on the stem by diagrams. 



D. THE TRICHOMES. These are of two kinds, the 

 hairs and the scales. 



i. The hairs. Notice 



a. The silky mass extending downward along the 

 midrib, serving for roots, rhizoids : the part of the 

 thallus from which they arise. 



1 The areolne and stomata are very large in Conocephalus conictis, the 

 latter being plainly seen without the aid of a lens. 



