320 ECONOMIO BOTANY. 



macrocarpa (family PhytelephadeoB, nearly related to PaZ- 

 macecB), a plant found in the tropical region of America. 

 The tree has a stem six or eight inches in diameter, 

 and pinnate leaves eighteen to twenty feet long. The 

 dioecious flowers are enclosed in a spathe; the cluster 

 of fruit is globular, six or eight inches in diameter, and 

 contains about forty nuts, each nut as large as a walnut, 

 ovate, slightly flattened, and contains within the brittle 

 shell the endosperm, which is nearly as hard as ivory; 

 it is composed of parenchyma, whose cells have very thick 

 walls. This, called Vegetable Ivory, can be readily turned 

 and colored, and is used extensively in the manufacture of 

 toys, buttons, handles, door-knobs, and other small objects 

 for which ivory Is used. 



GALLS AND qRYPTOGAMS. 



323. Galls are pathological, often more or less globular, 

 outgrowths on the stems, twigs, or leaves of many plants, 

 caused by the punctures or stings of insects. The best 

 Galls of commerce are collected' from an Oak of the 

 Levant, Quercus infeetoria ( Cupidifefrai). A species of Oy^ 

 ni/ps, an insect belonging to the suborder Hymenopiera, 

 inserts its ovipositor in the leaves and twigs and deposits 

 its eggs. An unnatural multiplication of parenchymous 

 tissue takes place, forming the excrescence or Gall with 

 the eggs, now hatched into larva, within. A large amount 

 of tannin is contained in the tissue, and the Galls are, 

 therefore, used in tanning, dyeing, making ink, etc. In 

 Europe a large quantity of Galls is obtained from Querem 

 pedunaulata and Q. sesdliflora. The Chinese Galls come 

 from a species of Sumac {Rhus). Curious red-horned 

 Galls, iised for tanning morocco leather, are obtained 



