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 



