216 PRACTICAL COURSE IN BOTANY 
united in this way, no matter what the number in each set, 
are said to be diadelphous, that is, in two brotherhoods. 
Notice the position of the lone brother, whether below the 
pistil — next to the keel —or above, facing the vexillum. 
Would the projection of the pistil, when the wings are de- 
pressed, be facilitated to the same extent if the opening in the 
stamen tube were on the other side, or if the filaments were 
monadelphous — all united into one set? Flatten out the 
stamen tube, or sheath, formed by the united filaments, and 
sketch it. 
240. The pistil. — Remove all the parts from around the 
pistil, and sketch it as it stands upon the receptacle. Look 
through your lens for the stigmatic surface (223). See if 
there are any hairs on the style, and if so, whether they 
are on the front, the back, or all around. Can you think of a 
use for these hairs? Notice how the long, narrow ovary is 
attached to the receptacle; is it sessile, or raised on a short 
footstalk? If the latter, label the footstalk, stipe. Select a 
well-developed pistil from one of the lower flowers, open the 
ovary parallel with its flattened sides, and sketch the two 
halves as they appear under the lens. Notice to which side 
the ovules are attached, the upper (toward the vexillum) or 
the lower, and label it, placenta. How many locules has the 
ovary? How many carpels? How can you tell (216)? 
241. Plan of the flower. — Diagram the flower in hori- 
zontal and vertical section, and decide upon the following 
points : — 
Numerical plan 
Symmetry 
Regularity 
Union of parts 
Position of the ovary 
242. Significance of these distinctions. — These distinc- 
tions are important to remember, not only because they are 
very useful in grouping and classifying plants, but because 
they mark successive stages in the evolution of the flower. 
In general, flowers of a primitive type and less advanced 
