684 POPULAR SCIENCE MONTHLY. 



possible, however, to deduce even from these precise criterions 

 anything but an approximate conclusion. Ferri points out 

 frankly, in the brilliant treatise that precedes his study of com- 

 parative anthropometry, the difficulties of such classification. He 

 insists, for example, that, besides craniological characteristics and 

 the qualities inherent in the individual and the race, due regard 

 must be had to psychological conditions. 



DOGBANE AND MILKWEED. 



By MATJD GOING (E. M. HAKDINGE). 



THE story of the trap-setting and insect-eating plants is a 

 more than twice-told tale. The pitcher- plant, which beguiles 

 the hapless fly to his drowning in its vase- shaped leaves, baited 

 on the outside with nectar-bearing glands, and filled with water; 

 the Venus's flytrap, which shuts up on him and crushes him ; the 

 sundew (Drosera), which chokes him in a sticky secretion, are all 

 known, at least by pictures and descriptions, to the tyro in bo- 

 tanic study. And we have learned that they all have good and 

 sufficient reasons for thus dealing with the hapless flies. For 

 " the plants grow," says Grant Allen, " in places where the 

 marshy and water-logged soil is markedly wanting in nitrogen 

 compounds. Insect-eating leaves are thus a device to supply the 

 plant with nitrogen by means of the foliage, in circumstances 

 where the roots prove powerless for the purpose." 



The insect slaughter which they carry on has the same excuse 

 as the animal slaughter of the abattoir. It is killing for food, and 

 the insects which these plants catch are honestly eaten and di- 

 gested. But in the infinite analogy of the vegetable world we 

 find a curious parallel to killing for sport. There are a few 

 native flowers which entrap insects simply and solely, it appears, 

 for the deed's own sake. The prisoners serve no apparent use in 

 the plant's economy, nor do their poor little corpses nourish the 

 plant's life. A botanist who let his imagination run away with 

 him might accuse the guileless-looking flowers of that savage joy 

 in another creature's pain which drew our forefathers in crowds 

 to the badger-drawings and bear-baitings of bygone times. 



One of these flower tormentors is the spreading dogbane (Apo- 

 cynum androscemifolium), which is common all summer, along 

 shady roadsides and around the borders of thickets, in the North- 

 ern and Eastern States. The plant is about three feet high, erect 

 and branching. The flowers are nearly as large as single blossoms 

 of the lily of the valley, " and are very beautiful," says Mrs. Dana, 

 " if closely examined. The corolla is bell- shaped and cleft, at the 



