46 



lower stamens are very short, bein^ much wider than long. 

 The summit of the peduncle and the flower axis are strongly 

 carved so as to throw the spur well backwards, giving the 

 flower a characteristic appearance, and this serves to limit 

 the insects visits much more than the mere length of the 

 spur." 



In regard to visitors Robertson says: "Really, the pro- 

 per visitors are Iwes which are small enough to use the beam 

 as a support; so that the bumble-bees and butterflies may 

 properly be classed hs intruders, even when they reverse. 

 For the proper visitors of the bearded violet we must look 

 to small bees, among which the Osmias are most important. " 



Many of the violets produce cleistogampus flowers. 



The order shows considerable variations 

 as regards msect visitors. Ihe com- 

 mon door yard weed Stellaria media Smith is adapted to 

 short-tongued insects while Vianthus, SaponoHa officinal- 

 is. Lychnis and others are visited by more highlj' special- 

 ized forms. In the more highly specialized form of flowers, 

 odors and colors are conspicuous. 



Saponatia officinalis, L. The Bouncing Betty, is a 

 common weed in places and is adapted to nocturnal Lepi- 

 doptera- Species of Sphinx are common here at Ames we 

 have observed, tiem oris thi^be. Sphinx Carolina, S. 

 Chersis, Philampelus, Deilephila dneata. The nectar 

 is secreted by a little ridge on the receptacle. Nectar is 

 contained at the base of the tube. The flowers are white 

 and have a strong odor in the evening. The cal^-x tube is 

 18 21 mm. long. The flower is strongly proterandrous. 

 The outer stamens protrude first, dehisce and spread apart. 

 Then the five inner stamens dehisce, the styles are still 



