686 POPULAR SCIENCE MONTHLY. 



by a large and miscellaneous company, it can be fertilized appar- 

 ently only by bees and perhaps by a few large flies. 



The milkweed is a peculiarly constructed and very highly 

 organized flower. The petals, five in number, fold back as soon 

 as the blossom opens and press their backs against the flower 

 stalk. Inside them, standing upright in a ring, are five honey 

 jars, or nectaries, of peculiar form. Each nectary is hooded, and 

 inside each is an incurved horn. Within the circle of honey jars 

 are the five stamens, which are fixed to the base of the corolla, and 

 stand in contact with each other, surrounding and inclosing the 

 pistil. On top of the ring of stamens is a large five-sided disk, 

 which keeps the pollen from being blown away, or wet with rain 

 or dew. The whole stamen system is like a little tub or firkin, 

 standing in the midst of the flower, upside down. Inside this 

 firkin are two green pistils, which will be two green pods. The 

 pollen of each anther is collected into an Indian-club-shaped 

 mass, which is fastened to a similar mass formed by the pollen 

 of the next anther. Thus the two connected pollen masses be- 

 long to two separate stamens. They are united by a tiny black 

 disk. This disk is set just above an opening between the stamens 

 which runs " clear through " to the pistil inside the firkin. The 

 fly or bee stands on the outside of the firkin, and, tramping about 

 there, gets her foot caught on the black disk which is glutinous 

 and pulls out (if she is strong enough) the whole affair, disk and 

 attached pollen masses. A bee will gather three or four of these 

 at once, and I have seen one buzzing away from a head of milk- 

 weed loaded with no fewer than nine. Thus encumbered, she was 

 for a moment held prisoner by the flower, unable to pull herself 

 and her burden loose. Following the custom of bees, she carried 

 the pollen masses at once to another milkweed plant, and perched 

 upon one of its flowers in exactly the position in which she had 

 stood when visiting the first. This brought the pollen masses on 

 her feet exactly into the slits running through the stamen ring 

 to the pistil. 



The bee seems the favorite guest of the milkweed. The pollen 

 masses come out at once at her tread, and are carried directly to 

 the pistil of another flower. 



Wasps visit the milkweed for its honey, but I have never seen 

 them withdraw the pollen masses. Flies seldom do, though the 

 flower is visited by flies of many species. Indeed, it is a general 

 favorite, standing in the midst of a winged throng till dark, for 

 twilight brings to it a number of small, dark-colored moths with 

 very long proboscides. 



But not all these visitors are permitted to go in peace. A small 

 fly with his legs stuck to the black disks is frequently unable to 

 pull himself loose after he has drunk his fill. On a bunch of 



