146 



INTRODUCTION TO BOTANY 



of the evening primroses, honeysuckles, and Jimson weeds 

 (fig. 131). The nectar from such flowers can best be reached 

 by insects with a very long proboscis, like that of the butter- 

 flies or the hawk moths (fig. 131). Many flowers with long 

 corolla tubes are also visited by humming birds. 



Red-clover flowers are pollinated 

 mainly by bumblebees. What effect 



FIG. 130. A, head of cab- 

 bage butterfly ; B, head 

 of honeybee 



a, antennae ; pr, proboscis, 

 or sucking organ. The pro- 

 boscis of the butterfly is 

 represented as coiled into 

 a spiral. Both somewhat 

 magnified. After Behrens 



FIG. 131. Pollination of flower of Jimson 

 weed (Datura) by a hawk moth 



The nectar is inaccessible to ordinary insects 



upon the crop of clover seed have field mice, which destroy 

 the nests of bumblebees? How would red clover thrive if 

 introduced into a country where there were no bumblebees ? 

 139. The arum ; a pitfall flower cluster. Our common jack- 

 in-the-pulpit is the most familiar American member of the 

 great (mostly tropical) Arum family. The over-arching hood 

 and the tube from which it springs inclose a club-shaped 

 axis on which are borne many inconspicuous flowers. Great 



