466 



THE RUBIALES 



aquatic in still waters and ponds. Certain leaves become modi- 

 fied into elaborate sacs with trapdoors for enticing and capturing 

 small insects which die and decay in these prisons and are ulti- 

 mately absorbed and so contribute to the nourishment of the 

 plant. The butterwort {Pinguiciila) is another member of this 

 family found in the northern countries and also in our southern 

 states. It has more the appearance of a violet with a rosette 

 of leaves which are provided with glands that secrete a viscid 

 substance for the capture of insects and also digestive fluids. 

 The contact of the insect acts as a stimulus, causing the leaves 

 to roll up and so bringing to bear upon him a larger surface 

 of digestive glands. One of the species of Pingiiicula is used 

 in northern countries to curdle milk in place of "rennet" which 

 contains the similar digestive fluids of calves' stomachs. 



The potato family (Solanaceae) shows many of the irregu- 

 larities of the figworts, but the majority of its 1,700 species have 

 regular flowers as illustrated in Fig. 334. While the family 





Fig. 334. Flower of the potato {Solanum tuberosum), showing the stamens 

 inserted on the tube of the corolla and encircling the style. 



is largely tropical, many of the species are cultivated, as the 

 potato, eggplant, tomato, cayenne pepper {Capsicum) . Poison- 

 ous, acrid and narcotic properties are characteristic features of 

 the family. Belladonna and atropine from Atropa, stramonium 

 from Datura and nicotine from Nicotiana tabaciim are character- 

 istic drugs. Ground cherry (Physalis), nightshade (Solanum), 

 Petunia, etc., are cultivated forms. 



153. A Transitional Order. — It would appear that all the 

 changes possible in the hypogynous type of flowers had been 

 wrought in the members of the Polemoniales and that the next 



