THE VIOLET FAMILY. 197 



III. Remove carefully the floral envelopes on one side 

 so as to expose the essential organs without disturbing 

 them. Notice the relative position of stamens and pistil, 

 and their structural peculiarities. The large, rounded 

 stigma with an orifice in front. The " lip " forming the 

 lower edge of. this orifice. The syngenesious anthers arid 

 their membranaceous connectives united into a tube just 

 back of the stigma. The two nectaries projecting into the 

 spur. The narrow canal lined with hairs leading from the 

 entrance of the corolla back to the spur. 



Jar the btamens and see where the pollen falls out and 

 where it lodges. 



IV. Go over all the structures again, in more than one 

 specimen, and see if you can determine the use of each 

 part of the mechanism. Imitate the action of a bee by 

 inserting a slender piece of quill or wood, pushing along 

 the groove down to the nectar cavity. Withdraw it and 

 see if it brings away any pollen. Insert it into another 

 flower and examine the stigma of the latter with a lens 

 before and after the operation to see if any pollen has been 

 left on it. 1 



V. Make a true longitudinal section of the flower (a 

 razor is best for this purpose), and sketch the parts in out- 

 line so as to show their relative position. Name and 

 locate each, using letters and guiding lines. 



VI. Make a transverse section of the ovary and examine 

 under a lens. Note 



1. The number of placentae. 



2, Number, direction, and form of ovules. If practi- 



cable, compare ripe capsules. 



1 Cf . Sachs, Physiology of Plants, p. 795. 



