134 



THE POPULAR SCIENCE MONTHLY 



anther is turned outward away from the stigma. This arrangement 

 will be seen in Fig. 4, which presents a longitudinal section of the 

 flower after the petals have been removed. It is as if you apply pow- 

 der to the surface of one sheet of paper and mucus to the surface of 

 another, and, intending that the powder should be brought into con- 

 tact with the mucus, place the two sheets together, surface to surface, 



Flower of an Iris, or Flower-de-Luce : 

 a, a, two of the three outer petals ; b b b, 

 the three inner petals ; c c. two of the 

 branches of the petal-like «?tyle. 



Fig. 4. 



A Longitudinal Section of Fig. 4: two 

 branches of the style beins: cut Ihrousrh, 

 show the plate-like stigmas a a, which 

 loop the anthers b b. 



but turn the powdered surface out. What a seeming design, and yet, 

 seemingly, what a fatal blunder ! But this is nature as manifested in 

 the iris. Pollen and stigma, so close together, are separated by the 

 blade of the stamen. But for insects which, attracted by the color, 

 light, and search the flower for its nectar, and push, now against an 

 anther and now against a stigma, the iris could never set a seed. 



Flowers, as Dr. Gray has said, seem to be made on the principle, 

 " how not to do it." By traps, and pits, and springs, insects are made 

 to do by indirection what it would seem could be better done directly 

 by the flower itself. For many flowers the service can be rendered as 

 well by one nectar-loving insect as another. But in some species the 

 parts are so modified that only a single species of insect, correspond- 

 ingly modified, can reach the organs of fructification. In the northern 

 part of the United States the yucca (Fig. 5) has never been known to 

 set seeds. 



An entomologist has lately discovered a small moth with white 

 head and thorax and wings, and legs of dingy yellow. To this moth 

 he has given the name Pronuba yuceasella — yucca's go between. The 

 structure of this moth will be seen in Fig. 6. In Fig. 1 the larva 

 and the moth are drawn in the natural size. The peculiarity of this 

 moth is, that in the female the basal joint of one of the maxillary palpi 

 (Fig. 6, 5) is modified in a most wonderful manner into a long prehensile 



