67 



lower Hymenoptera. Zizia, Poly taenia and Eryngium agree in 

 showing a "preponderance of Hymenopera over files as an 

 efiiect pf concealment of honey. Pastinaca,' Gicuta and 

 Slum show the same result as an efl\jct of time of blooming. 

 Forms with hidden nectar also show marked contrasts on ac- 

 count of time of blooming. Thus, in the case of Zizia 

 which blooms in May, one-half of tiie Hymenoptera &re bees, 

 while in Eryngium.^ which has more deeply-seated honey 

 but blossom in July, only one-third of the Hymenoptera are 

 bees." 



Cow Parsnip. This large, coarse perennial grows in 

 deep, rich woods and bears large and broadj white '^umbels. 

 The larger plants have two or three secondary umbels and 

 one of the third order. Robertson gives the proportion of 

 male and hermaphrodite flowers in different umbels as fol- 

 lows: "First order, o male and 420 hermaphrodite in nine- 

 teen umbellets; Second order, one hundred and twent}' 

 male and three hundred and three hermaphrodite flowers in 

 twenty umbellets; Third order, three hundred' and eighty- 

 nine male and forty-six hermaphrodite flowers in twenty um- 

 bellets." From this table it will be seen that those of the 

 first order are entirely hermaphrodite while those of the third 

 order are almost entirely male. The same relation is borne 

 out here at Ames. The hermaphrodite flowers are proteran- 

 drous. It is abundantly visited by Diptera, especially Syr- 

 phidae and by some Hymenoptera as the honey bee. In the 

 Rocky Mountains, where I observed the plant, small Hy- 

 menoptera and Syrphidae were common. 



The order shows considerable variation as 

 regards pollination. On the one hand it 

 is well adapted to Lepidoptera, Sphingidae, birds, and long- 

 tongued Hymenoptera, and on the other, in case of Adoxa 



