156 JOHN H. LOVELL 



Another common flower selected by Plateau for experiment 

 was the edible garden pea, Pisum sativum L. The flowers are 

 rarely pollinated by insects, and self-fertilization is almost in- 

 variable. It was for this reason selected by Mendel for his 

 celebrated experiments in hybridization. He says: "Among 

 more than 10,000 plants which were carefully examined there 

 were very few cases where an indubitable false impregnation 

 had occurred." » During four summers, however, Muller 

 frequently saw the flowers visited by both sexes of Megachile 

 pyrina, and the females both sucked nectar and collected pollen.^ 

 Plateau's observations were confined to walking on two occasions 

 through many cultivated fields of peas, in one of which he saw 

 a single Bombus agrorum. 



Plateau introduced anisette into a dozen, or, on one day, two 

 dozen flowers of Pisum sativum growing in his garden, which 

 were carefully observed for from one to three hours on five days. 

 The anisette was renewed_ each day. Twenty visits were made 

 by species of Bombus and Megachile] and ten visits by flies and 

 small bees which could not possibly effect pollination. Plateau 

 attributed the small number of insects attracted by the odor- 

 iferous liquid food to frequent interruptions by rain. 



The flowers of the common garden pea are rarely visited by 

 insects, not because they are nearly odorless and the coloration 

 is of no value, but because of the difficulty of depressing the carina. 

 This species no longer exists in the wild state; and, according 

 to De Candolle, was probably introduced into Europe from 

 Western Asia. *« Muller says: " In its original home the pea no 

 doubt adapted itself to some strong and at the same time diligent 

 and skillful species of bee, which could easily depress the carina, 

 and was plentiful enough in ordinary weather to act as the regular 

 fertilizing agent. Under such conditions, the advantages of 

 firm closure would outweigh the disadvantages. In our climate 

 the pea fails to find bees adapted to its flowers, and it would be 

 much better for it under these altered conditions to have its 

 flowers less firmly shut." »» 



During the summer of 1912, I saw the flowers of the garden 



"Bateson, W., "Mendel's Principles of Heredity," p. 342. Bateson is of the 

 opinion that Thrips may be a source of error. 

 » Muller, H., " Fertilization of Flowers," p. 214. 

 » De Candolle, A., " Origin of Cultivated Plants," p. 329. 

 « " Fertilization of Flowers," p. 214. 



