ANIMALS AS FOOD, FOES, OR FRIENDS. 269 



231). In others, portions of the internodes are much en- 

 larged and hollow ; sometimes only the internodes in the 

 region of the flower clusters are thus transformed. In other 

 plants chambers are produced by the bladdery enlargement 

 of the under part of the leaf near the midrib (fig. 232). In 

 some acacias the stipules are developed 

 as large hollow thorns, which the ants 

 inhabit. a— 



381. 5. Crystals. — Plants protect 

 themselves against soft -bodied animals, 

 such as snails and slugs, by means of 

 the sharp-pointed crystals which are 

 present in the leaves of many species. 

 According to Stahl, all tissues contain- 

 ing these crystals are avoided by such 

 animals, but will be readily eaten by 

 them after the crystals are removed. 



382. Summary.-Carnivorous plants ^.^ ,3,._u„der side of the 

 use small animals, especially insects, base of the leaf blade of tv?- 



' ^ J f coca lancijolia, showing 



as food, capturing them by pitfalls, bladder on each side of mid- 



' ^ ° J jr 7 no, each with entrance at 



traps, or adhesive surfaces, and either g."- Natural size (?j.— After 



■^ ' ' Schumann. 



digesting and absorbing the useful parts, 



or after the slower decay, absorbing certain substances. Many 

 plants protect themselves against browsing animals by armor, 

 by distasteful or injurious juices, by mimicking distasteful 

 or hurtful plants, or by harboring fierce ants which attack 

 anything that disturbs the plant they have made their home. 

 For the ants some plants provide not only shelter but food. 



