206 PRACTICAL COURSE IN BOTANY 
Remove the perianth and sketch the remaining organs in 
profile, showing the position of the stamens. Do you see 
any advantage in their position? Can you determine the 
use of the crest of hairlike filaments on the upper side of the 
sepals? Remove a stamen and sketch it. 
223. The pistil.— Remove as much of the upper part of 
the perianth tube as you can without injuring the pistil, 
and with a sharp knife cut a vertical section down through 
the ovary so as to show the long style and its connection with 
the placenta. Make a sketch of this longitudinal section 
(see Fig. 291), labeling the parts observed. Notice whether 
the placenta is central or parietal. Draw a cross section of 
the ovary; how many locules has it? How many ovules in 
each? Where are they attached? Is the placenta free 
central or axial (Fig. 293)? Examine with a lens the little 
flap at the base of the two-cleft apex of one of the stigmas, and 
look for a moist spot to which the pollen will adhere. Label 
this in your sketch, stigmatic surface. No seeds can be ma- 
tured unless some of the pollen reaches this surface; can you 
think by what agency it is carried there? What insects 
have you seen hovering about the iris? Notice that in 
drawing his head out of the flower, an insect would not 
touch the stigmatic surface, since it is on the wpper side of 
the flap and he would be probing under it. But in entering 
the next flower that he visits, he is likely to 
. strike his head against the flap and turn it 
under, thus dusting it with pollen brought 
‘@) from another flower. 
224. Diagrams. — Draw diagrams show- 
ing the horizontal and vertical arrangement 
Fic. 294.—Hori- of parts in the iris or other specimen ex- 
fontal diagramofiris amined, and compare with those made of 
the monocotyl studied in the preceding sec- 
tion. In what respect does it differ from them? How do 
you account for the difference in the number of stamens, if 
there is any? (220.) 
